I wonder if has anything to do with what kind of stuff you've selected for copying. I've had situations if selections including graphic elements or crossing style boundaries would do funky stuff in copying into the clipboard. Also ran into occasional issues when copying from one app and pasting into another -- especially if I'm dealing with different language text. Sometimes this involves making sure that the IME is set configured to the correct language (sometimes the IME is selected to the wrong language for a given app), and other times the only way I can get correct behavior is to change the setting in the Windows Control Panel for non-Unicode apps to whatever language I'm dealing with.