I'm using a Microsoft IntelliMouse Optical on Windows 7 x64 with whatever basic default drivers it loads, and lately I've had an annoying issue where the sensitivity would change out of the blue, being cut to maybe 25% of what it's normally at. I thought it was related to a particular game (Civ 5 and/or SC2); but it happens outside of the game and some searches have turned up nothing mentioning them being related.
When the sensitivity drops, adjusting the sensitivity in the control panel down then back up does nothing, the only thing that appears to fix the issue is unplugging/replugging the mouse, coming out of suspend or restarting.
Aside from some basic programs that run all the time (e.g. Google Talk, etc), I can't figure out any obvious connection.
As it's probably impossible to come up with any sort of fix without first knowing what's the cause, how can I go about looking for the possible source of this issue?