just a thought, go into (ingame) options, click on detail.
make sure your FPS cap is not low. happens to me all the time. i'm on win32 also.
should be set to 60 for most any laptop.
the game engine automatically reduces my FPS cap whenever there's a stutter, but doesn't seem to take loading time into account.
so every time i start PS, i have to resest the cap or the game engine lags, mouse doesn't work right, etc.
good luck.
laters,
b