I don't seem to be able to copy and paste any more. Not sure what I did to cause it.
I've tried doing it in several programs, including notepad.
Is there a quick and simple fix for this problem, that doesn't involve restarting my pc?
None of the above solutions worked for me. This one however did: http://sys-talk.blogspot.com/2009/04/clip-board-not-working-in-windows-xp.html (I am pasting the urls from the browser:) ) Generally, this tool locates an app that is holding the clipboard. For me, it was Xserver. For you, who knows.
Windows Notepad may be unable to handle excessively large content, or content with special characters. Although Notepad will generally strip out unsupported character set encodings or control characters, it is first and foremost a simple text file editor.
In my case, I had pasted a large amount of code from my development environment, which apparently overwhelmed Notepad. Even running the command to manually clear the clipboard failed. [cmd /c "echo off | clip"]
As per Mathew Lock's suggestion of an Application that had locked the Windows clipboard, I narrowed down the culprit to that of Notepad. Immediately upon terminating my NOTEPAD process, the lock on Windows Clipboard was freed.