copy and paste in windows XP just stops working

What I found:

This has to do with some application that's having a lock over the Windows Clipboard. David Candy's application should determine the Process that's causing the problem.

Download GetOpenClipboardWindow.zip from here: > http://windowsxp.mvps.org/temp/GetOpenClipboardWindow.zip

Unzip and run the tool. Post back what it reports. For best results, run this utility during the time you encounter the Copy<=>Paste problem.

So it might be some program is locking your Clipboard. Try to find out what's causing the problem and let us know.