Internet keeps crashing every couple of hours, please help!!!

Hello,

I’m having a major problem with my network.  Any help will be greatly appreciated.  

First off let me tell you the setup I currently have at the office.  I’m using Time Warner - Road Runner as my ISP, using a static IP address.  I have the Road Runner cable modem/router connected to the internet port on a Linksys BEFVP41 router.  In the linksys router web interface I provided all the static info that my ISP provided me with (IP address, DNS servers, Gateway, etc…), so the IP address in the linksys router never changes.  

I then have a server running windows 2000 server connected to port 1 on the linksys router.  The linksys router also has a cable from port 2 connected to port 1 on a TrendNet switch.  This switch then connects the rest of my computers to the network ( I have 11 computers plus the 1 server connected to the network).  

I have DHCP disabled on the Linksys router, and I’m using the DHCP server and DNS server on the windows 2000 server.  The server also has a internal static IP address (192.168.1.10), and the default gateway points to the Linksys router (192.168.1.1).  The primary DNS for the server is itself (192.168.1.10), and the secondary DNS is one of the IPs the ISP provided me (66.80.x.x).  

Ok, now with this setup everything seems to run fine for a couple of hours and then the internet just crashes.  Users still can use the network drives on the server, but all internet access is blocked.  When this happens the activity light in the network closet usually starts blinking very rapidly.

I’m running Symantec Antivirus Corporate Edition 8.1 on the server and the definitions are all up to date.  Each client pulls the definitions from the server, so they’re all up to date as well.  

I ran a scan on all computers and on the server and it did find some viruses which it then cleaned out.  I also ran SpyBot and Lavasoft Adaware which also found malware and spyware and it cleaned it out.  In addition to the Symantec scan I also ran the online scan  HouseCall Trend Micro, which found some viruses and cleaned them out.

All computers and the server are running the latest service packs.  I don’t know what else could be causing the network to keep on crashing.  I’m running out of ideas.  The only thing I can think of is that there’s still some type of virus on one of my computers that’s causing a DOS attack.  

One other thing, when the internet crashes like that and I unplug either the server or sometimes it works with unplugging another computer from the network.  Everything seems to go back to normal, the lights start to blink at a normal speed and there is internet again.  Very Weird!!!!

Does anybody have any ideas on what I should do?  Or is there some type of software that could help me find what the problem is?

Thank You,
DaliSalv22