I experienced this problem after installing some Logitech software for a universal remote. The installation process required my administrator password, which I did not like. Logitech has a reputation for troublesome installs. At any event, I lost the ability to copy and paste. Nothing would go to the clipboard. I also noticed that I could not drag an application from a mounted disk image to the Application folder.
I tried the permission repair/disk repair/restart routine with no effect. Since the problem began after installing software, I suspected a problem with update of prebinding. This Terminal command followed by a restart, did the trick and restored copy/paste at once:
sudo update_prebinding -root / -force
Message was edited by: David Cross