can not login to server as an administror

Is this server a member of a domain? If so, can you try accessing the server with a Domain Admin account?

Happened to me once and I spent a couple hours trying to figure it out. Turned out the KVM Keyboard had a bad key.

What error if any do you get when you attempt to login into the 2008 server?

Are you able to use those credentials and access any other server on the network?

Are you able to use your own account to login into the 2008 server?
If so you can elevate your rights using runas /user:<administrator account> cmd
and then launch what you need.

Perhaps the administrator account is being prevented from being used interactively via GPO?

I have one account which is the administrator . when i enter the password it say wrong password or user . i did check the keyboard is ok.

on the same lan when i try to connect to the server on remote connction . it does connect me and when i enter the password and user id it does accept that too and take me the server main screen which is lock up with the alt+ctrl+del key and there it does not accept the password .

Unfortunately, I am no getting the picture of what you are doing.
Make sure that the session that you are connecting to remotely is not connected to another remote host.

Are you sure you are logging into the domain account and not a local account. You can make sure by doing this, adding the domain to the username in the username field
domain-name\user-name
example
happiness\lmm

I am entering as
my domain name is poffice
so i m entering as poffice\administrator
and then the password . but i am getting wrong username or password . I am sure nobody change  as no one has access to that computer room except me. I did try some utility in order ot know the password in case  or reset but does not work . please help me thanks

Do you have a second user you can use, one that is an administrator and a domain admin? If so, logon with that and reset the password

Can you login using this account to any other system?
If you can login, you could use GPMC to see what is preventing this user from logging in, you can then also use eventlog to access that server's eventlog and see why your credentials are being rejected.
Create a separate account and see whether you can use the new account to login into that server and then use the runas /user: to elevate your rights.
try using administrator@poffice as the login.

Use compmgmt.msc to look at the local group/user to make sure this domain account is not part of a group.

The main issue from your comments is that the user/password combination is what causes this system to reject your login.  Is this a DC?
Double check that all the DC's in the environment are synch up using dcdiag.

poffice\administrator--are you use administrator is spelt correctly? I have done that from time to time

I will do check that also . I did restart the server and now first messgae i am gettingt hat "there is a time  and/or date difference between the client and the server" . Also I have been using the same password from more than an year now . It was working fine .

Also I can log in with the password using safe mood . but can not do any changes

If the time is way off you will have issues

In safe mode, you should be able to adjust the time/time zone which might be the issue or the internal battery is messed up.
During bootup, get into the bios and set the correct time.

I did log-in safe mode . I did reset the administrator password too. the time zone and  the date etc are correct. still when i login in n normal mode it keep saying the saying date and time are in clinet and server difference. it seems that there is some thing in time synchornization. when I login and enter the password it seems like it accept but right after entring the password it give me time differnce message .

is there a way where i disable the time checkup etc

No, in a domain login, the time is included as a check. i.e. a packet from days ago will not be accepted as valid.
 
Did you check the timezone on the server?  Since this is the only server/system that has this error, I suspect that this server is at fault.

i did check the time zone which is correct . Also i did confirm the date and time in bois it has no problem at all .

FYI--not sure how often you use experts exchange but it is standard practice to award 250 to 500 points for answering questions--you are only awarding 50. You may have assumed when you asked the question that it would be quick and easy and that is why you only gave 50 points as a reward but as you can see it is taking much more time and efforts on the experts behalf to only award whoever gives you the right answer only 50 points. And even if you did get a quick and easy answer I believe it is good practice to offer at least 250 if not 500, rewarding experts for their time and efforts for your questions in particular and sometimes for their past experiences and knowing the right answer right away.

That been said--so is there no way you can now logon to this server, either locally or remotely and not with any user? Is that correct?

Is this the only system that has this issue?

Disconnect the system from the network and see if you can login in normal mode.

Dear lionelmm:
you are absolutely right . the points its just a mistake of selection or typing. I will correct that and sorry for the inconvinece . you guys deserve more no doubt about it . sorry once again .

I can conncect to the server in lan by entring the ip address in internet explorer and can access the shared directories..
i remote i can reach till the login screen  but does not accept the passowrd
some time it does accept the password but right aftger that the "error of time and difference comes"
i can enter with the same password in safe mode.
i did disconnect it from netowrk but the same problem

yes i have only one system which does this.

Can you manually set the time/date on the server by using psexec from another workstation?

How are you remoting into the server? What are you using? Remote Desktop Connection? In an earlier comment you said you are on the same LAN but even on the same LAN it will not accept the crdentials--so are you able to go the server console and logon directly? Also try this from your PC--from a DOS window run Net Time \\ProblemServerName /set /y to see if that will fix the time issue between you and the server--this will set your time to the time on the problem server.

As it was sub domain and the main controller has a wrong date . when i correct that date and time and then i just recreate the password it .work . thanks all of you .