Originally Posted by Freebase Dali

It could very possibly be a keyboard problem.
I know that the keystroke cntrl+prtsc copies screen images into the clipboard. Unless there's something wrong with your clipboard itself (Which Tore is having a problem with right now, in Windows 7, so it's not beyond belief) then a keyboard problem could be likely.

Just to be sure there isn't some kind of weird software clusterfuck, restart your computer an attempt to capture your screen image again. Paste it in Paintbrush. Let me know what happens.