Just for troubleshooting purposes - could you use a wired USB mouse?
I ordered one but it won't be here til tomorrow.
Do you think this could be it? I was suspicious it could be related, that's why I included it in the OP. I can't remember the model of the mouse off the top of my head but it's supposed to be crazy high-featured, at the time it was advertised as "the world's most advanced mouse".
Will update tomorrow or if anyone has any other ideas I can try in the meantime