Just a suggestion but....
Do you have a wired xbox 360 controller? Or a similar game pad for that matter. It works out of the box with windows 7. There are a few 3rd party configuration programs that hot key the keyboard/mouse to the controller for older games, that dont have gamepad support. Not for nothing, but using such a program, may inadvertently 'fix' your mouse issues with the game. It's worth a shot. Joy 2 Key
is a freeware. Pretty limited though, according to the description.
(not my first choice.... may work, I have never actually used it.) Xpadder
is a easy to use freeware app. Has a decent fan-base. Plays well with most Pinnacle Game Profiler
is a more advanced, feature rich program. Costs $, but has a 30 trial. Works with 360, ps3, Wii, and most generic controllers. HIGHLY recommended.
(best $20 I've ever spent on software, let me tell ya)