[ QUOTE ]
Do you have a remote desktop session open? If so, close it. Otherwise try rebooting.
[/ QUOTE ]
Is this for specific content or anything you try? Like if you type something in notepad and ^c ^p in notepad will that work?
If that doesn't i would scan for spyware and viruses. There are a couple like this:
http://securityresponse.symantec.com...an.kility.html
that disable paste.