Quote Originally Posted by Ughmahedhurtz
I use Multiplicity 1.x for special mouse cases but everything else is hardware. I've seen it happen maybe 3 times, but that was usually because I had the run key held down when I moused off one PC and onto another one.
I would not be surprised to learn that this was in fact the reason this happens. I thought it was a software issue at first (like Keyclone or Synergy) but now that we have had a few responses from people that don't use software I think it may be something along these lines.