Thanks so much, I'll give it a try as soon as I get home. I thought I'd unchecked the clipboard option, but I may not have.

This may be completely wrong, but the impression I got when the problem occurred was that it only happened when I didn't move the mouse from one PC to another for a few minutes. For example, I never noticed the problem while going back and forth - only after I'd been on my primary for a few minutes, then tried to move the mouse back to the laptop. Is it possible that there is some kind of inactivity timeout going on?

Thanks again!