Vista - Erratic mouse

Windows Vista Ultimate, 32 bit version. All updates installed.

I've been using a basic Microsoft USB wireless mouse the entire time I've
had Vista on this machine. About a week back it started having some
problems. Wouldn't always scroll when the scroll wheel was turned, didn't
always select when a button was clicked, even though I heard the switch in
the mouse click, and didn't move correctly, lagging behind the move I was
making or, sometimes, not moving at all. This seemed to start back around
the Microsoft updates last week, though I'm not prepared to blame them, in
part, because McAfee updated at the same time.

I changed the batteries, and it didn't help. So, I figured the mouse had
just had it. Bought a new one and still have the same problems, but with
one change. Whereas the old mouse rarely worked right after the problem
started, the new one often does work right. Difference may be that I never
installed the Intellipoint package for the old mouse, but I did when I put
in the new mouse. Or maybe that's got nothing to do with it.

I don't have a restore point that'll take me back to before the updates a
week ago, so I can't try that. The ones from this week didn't change the
behavior, so I'm not seeing any point in trying to back them out.

Ideas?

- Bill