In side of the systems event log is there a warning or error message recorded when this happens? If so what is the message and event ID number.

I have seen this happen one other time at my work place and the issue was a piece of spyware that re-mapped the keyboard commands. The way I fixed it was to roll back the drivers and reinstall them for what every keyboard you are using. I’m not sure if this will help you out or not but it is worth a try.

Here is some other information that will help us to attempt to figure out your problem.

Windows Version
Event ID
Is it a Wireless Keyboard?


Also this link may help you out
http://www.microsoft.com/windowsxp/u...t/nostart.mspx