^Malware exists, if you believe the propaganda that it doesn't you'll eventually get something. And the bad thing is that you'll have to have given it complete permission to do so - so it will more likely be a rootkit or something equally nasty.
Did you get your clipboard to work? If not, or if so, for reference try this. Go to start>run and type clipbrd. Up to Edit and delete. This will empty it and should resolve the problem without needing a restart.
If that doesn't resolve it, do a thorough scan for malware. You can also manually check your registry because there can sometimes be a string that pops in there (usually from malware, but sometimes from legit apps) that can mess it up. If you want to know where to look and what to look for, ask and I'll share.
Third, it could simply be that a window file corrupted. This happens over time from filling up your hard drive, improper shutdowns, driver/software issues, and everyday use. This isn't necessarily a windows problem, though it's more prone to it, but is just what happens when we use an installed OS day in and day out.
If a file corrupted you simply need your windows disc to fix it.
And finally, if you have a special keyboard that you had to install a driver for, it could be that. Though less likely.
