The master browser has received a server announcement from the computer that believes that it is the master browser for the domain on transport NetBT_Tcpip_A563D8D5-4C37-4BD2-B6. The master browser is

http://www.winguides.com/registry/display.php/54/

Control Network Browser Elections (Windows NT/2000/XP) Popular
A browser election is a normal network occurrence and provides a means to guarantee there is never more than one master browser present in a domain or workgroup.

 This tweak can be easily applied using WinGuides Tweak Manager.
Download a free trial now!

Open your registry and find the key below.
To control which computer is the Domain Master Browser, create a new string value, or modify the existing value, named "IsDomainMaster" and set the value to equal either "Yes", "No" or "Auto".

To prevent an NT Workstation or Server (non-PDC) from acting as a browser, create a new string value, or modify the existing value, named "MaintainServerList" and set it "No", the other options are "Yes", "No" or "Auto".

Restart Windows for the change to take effect.

Note: These values may also be standard boolean values in the form "True/False" or "0/1".

Registry Settings
System Key: [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Browser\Parameters]
Value Name: IsDomainMaster, MaintainServerList
Data Type: REG_SZ (String Value)

On the other mahcine(s) set the IsDomainMaster to no

Is that the reason Why  Network beome  too slow? User's can't  connect  althought  it was  fine till morning.

Quite Frankly I don't know. You could possibly have a NIC that is misbehaving like maybe it has gone bad or the drivers just need to be reinstalle etc

http://support.microsoft.com/?kbid=191611
http://support.microsoft.com/?kbid=188001

As for the slow connection, look for spyware/adware:

SpyBot-S&D

SpyBot-S&D is an adware and spyware detection and removal tool. This includes removal of certain advertising components, that may gather statistics as well as detection of various keylogging and other spy utilities. In addition, it also securely removes PC and Internet usage tracks, including browser history, temporary pages, cookies (with option to keep selected) and more. The program offers an attractive outlook-style interface that is easy to use and multi-lingual. SpyBot-S&D allows you to exclude selected cookies, programs or extensions from being reported, allowing you to prevent false positive messages for items that you dont want to be alerted of every time. It can even scan your download directory for files that have been downloaded, but not yet installed, allowing you to detect unwanted programs before you even install them. SpyBot produces a detailed and easy to understand report before it deletes any files and allows you to deselect any item that you do not want to be processed. In addition, a recovery feature allows you to restore your settings if needed. Very nice tool, that exceeds the capabilities of the popular Ad-Aware application.

http://www.webattack.com/download/dlspybot.shtml 

Ad-aware

AdAware is a privacy tool, that scans your memory, registry, hard, removable and optical drives for known data-mining, aggressive advertising, and tracking components. It then lists the results and offers to remove or quarantine the components. The program detects a wide range of adware/spyware related issues and can be updated with the latest signatures via the built-in update utility. Please be advised that removing certain components may impact the functionality of effected software applications. You should fully read the included Ad-aware documentation before removing any files!

http://www.webattack.com/download/dladaware.shtml 


HijackThis

HijackThis is a tool, that lists all installed browser add-on, buttons, starup items and allows you to inspect them, and optionally remove selected items. The program can create a backup of your original settings and also ignore selected items. Additional features include a simple list of all startup items, default start page, online updates and more. Intended for advanced users.

http://www.webattack.com/download/dlhijackthis.shtml 

Keylogger Hunter

Keylogger Hunter is a program that attempts to detect any keyloggers that may be running on your computer. It performs a system analysis, which takes about 3-5 minutes and then produces a list of suspicious files (if any). It detected 2 out of 3 running keyloggers in our test. Future versions are planned to be shareware.

http://www.webattack.com/download/dlklhunter.shtml 

KL-Detector

KL-Detector is designed to provide a way to find out whether your activity is being recorded with a keylogger application. It uses the fact that most keyloggers create a hidden log file on your hard drive and therefore scans for any suspicious activity during a test period that you have to initiate. Basically, it asks you to use the keyboard for several minutes, type some text or do similar activities, while it is monitoring your system to check if it can detect any suspicious logging activity. KL-Detector is intended for occasional use and not as a permanently running program, as normal PC activity may cause false positives. During our test, it did detect changes in a keylogger log file (that we installed), but it did not find the activity suspicious enough to warn us. Advanced users may get value by inspecting the logged items, however novice users should not rely on the results.

http://www.webattack.com/download/dlkldetector.shtml 

X-Cleaner Free

XCleaner is a privacy tool suite that detects and removes installed spyware and adware components and includes tools to securely delete files, edit the registry, disable startup programs and more. Additional features include IE home page protection, cookie, cache and history cleaning, built-in password generator and more. This free version also contains some additional feature options, however they are disabled and require upgrade to a full version. The spyware and adware scanning as well as many cleaning features however can be used freely.

http://www.webattack.com/download/dlxcleaner.shtml 

SpywareBlaster

SpywareBlaster doesn`t scan and clean for so-called spyware, but prevents it from being installed in the first place. It achieves this by disabling the CLSIDs of popular spyware ActiveX controls, and also prevents the installation of any of them via a webpage. This allows you to run Internet Explorer with Active-X enabled, but it will never download or even prompt you for any of the known ActiveX controls. All other Active-X controls or plug-ins will work fine. The SpywareBlaster database contains information on these known spyware Active-X controls and can be updated with the click of a button. The application windows displays a list of all controls that it is able to detect (this is not a list of what was found on your computer). The program cannot detect if you have any of the known objects already installed, but if you do, they will be disabled. The program also allows you to take a snapshot of your computer (certain settings) in its clean state and later revert many changes made by spyware and browser hijackers.

http://www.webattack.com/download/dlspywareblaster.shtml 

SpywareGuard

SpywareGuard provides a real-time protection solution against so-called spyware. It works similar to an anti-virus program, by scanning EXE and CAB files on access and alerting you if known spyware is detected. If this is the case, it initially blocks access to the file and then allows the user to select an action. SpywareGuard provides a fast scanning engine, signature-based scanning, heuristic/generic scanning, a control panel, and an online-update utility for downloading of definition updates. It does not replace your anti-virus protection, but instead detects programs that may cause privacy concerns. The list of detected programs includes AdBreak, AdultLinks/LinkZZ, Brilliant Digital, CommonName, Cytron, FreeScratchAndWin, FriendGreetings, HighTraffic, HotBar, IEDisco, iGetNet, Lop.com, MoneyTree Dialer and others.

http://www.webattack.com/download/dlspywareguard.shtml 


SpySites

SpySites allows you to manage the Internet Explorer Restricted Zone settings and easily add entries from a database of 1500+ sites that are known to use advertising tracking methods or attempt to install third party software. You can select the sites from the list, or optionally add all of them, or only the "worst offenders". The program then adds the URLs to the IE Restricted Zone settings. Once configured, there is no need to run the program again, unless you want to add additional sites.

http://www.webattack.com/download/dlspysites.shtml 

Along with jvuz thinking

Double Check for viruses
Online Scanners

 Norton Web Services  
Go to this page and click on Scan for Viruses
http://security.symantec.com/ssc/vc_about.asp?j=1&langid=us&venid=sym&plfid=22&pkj=REODSKVYRMHCGVRVRMN

It needs to download a few file so as to activate the scan so you may see a message like this.

"The Scan for Viruses uses an ActiveX program to scan your computer. The download is approximately 1.5MB and can take about 10 minutes over a 28.8 modem.

The scan can take more than 20 minutes depending on the speed of your computer and the number of files that you have. Please do not browse away from this page unless you intend to abort the scan.
 
Downloading Scan for Viruses controls. Please wait...
 
During the download, you might see one or more messages asking if it is OK to download and run these programs. Click Yes when these messages appear.
 
Note: Scan for Viruses does not scan compressed files"

======================
 Trend Micro HouseCall        
www.housecall.antivirus.com
"Trend Micro's free online virus scanner
In order to better serve our customers, we ask HouseCall users to register before scanning their computer.  By registering, you will receive virus alerts from our team of Virus Doctors. You will be able to unsubscribe when you receive your first email. You can also scan without registering"
http://housecall.antivirus.com/housecall/start_corp.asp

======================
eTrust Online antivirus scanner
http://www3.ca.com/virusinfo/virusscan.aspx
======================

PC Pitstop Virus Scan
Our free Web-based virus scan uses Panda Software's award-winning technology and virus list. We're checking against the "wildlist," the roughly 200 viruses that are most prevalent in the world in a given month
http://www.pcpitstop.com/antivirus/default.asp

Paranoid people.
There is nothing wrong, this is typical behavior on an NT  domain.

No it's not typical behavior on an NT domain. In my case I had several computers, both XP workstations and member servers, constantly forcing elections because my PDC would not hold the Master Browser role.

Adding the suggested registry entries fixed the problem.