Well, took the battery cover off. closer inspection showed that
one of the duracell procell battery's had Grey goo hissing out of the
positive end of the battery. I have NEVER seen a AA battery do that
before. replaced the battery and the mouse was fine. Go figure...
They were some I had laying around with a 2008 code date on them.

I've had Duracells leak in two pieces of equipment I own. It damaged one of
them, and Duracell had to replace part of the item (an Olympus dictating
machine).

I don't use Duracells. I use Eveready and Toshiba.