You have a problem with a corrupted user profile as the first thing to look at
http://support.microsoft.com/default.aspx?scid=kb;en-us;555021 QUOTE:
"CAUSE
Your user profile is corrupt.
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RESOLUTION
Before continuing, make sure you have backed up the contents of your My Documents folder, and any other important data stored in your profile such as application settings. Once your profile is deleted, you will not be able to recover data stored inside of it.
In order to delete your profile, you must be logged in with an account which has administrative privileges which is also not yours. Once you are logged in, open the user profiles list. To locate the list of local user profiles, right-click My Computer, click Properties, and then on the Advanced tab, click Settings under User Profile. Select your profile from the list, and then click Delete.
Logoff, and then log back on as yourself. A new profile will be created when you log on.
CAUTION
If the corrupted profile is that of a domain administrator, and it is located on the first domain controller in the forest, the EFS recovery key must first be backed up. See KB Article 324897 for details on this procedure."
There are also trojans especially if the "csrss.exe" file is discovered in other then the C;\Windows\System32\ subfolder.
"Process File: csrss.exe
Process Name: Microsoft Client/Server Runtime Server Subsystem
Description: csrss.exe is the main executable for the Microsoft Client/Server Runtime Server Subsystem. This process manages most graphical commands in Windows. This program is important for the stable and secure running of your computer and should not be terminated.
Note: csrss.exe could also be a process which is registered as a trojan. This Trojan allows attackers to access your computer from remote locations, stealing passwords, Internet banking and personal data. It could also be a registered security risk and should be removed immediately.
Determining whether this process is a virus or a legitimate Windows process depends on the directory location it executes or runs from in WinTasks."
http://www.processlibrary.com/directory/files/csrss/