Acer 6920g sudden freezing

Hi there
I seem to have a very weird problem where, sometimes when im gaming and only once or twice when its just idle or browsing internet and such, the computer semi-freezes for a minute or so.
What i mean is that the processing light (top one of the 3 lights beside the power button) is blinks continuously... i can move my mouse, i cant click or close anything, BUT i can open the start menu (meaning its not completely frozen.) When im in-game, the game freezes.... and the processing light just blinks like mad. After about 1 min or so everything that i did during the frozen period occurs at once (e.g opening folders, closing windows etc.) and it just goes back to normal functioning.
I can cope.. but sometimes in the middle of online/multiplayer games and it does that, 95% of the time ill disconnect, or the game crashes and ill have to reopen which is kinda frustrating.
I have no idea what the cause is. Im pretty sure it isnt the temperature because i had Real-temp runing and my GPU and CPU levels were normal (In-game GPU 60C CPU 25-35C, however my might be bugged coz at idle its insanely low)
One theory is that the graphics driver bugged up or crashed or something but i have no idea how to check coz if it freezes in game i cant tab out (or do anything but wait)
Another thing, i believe this all started after clean install of Win 7... but i dont think anyone else with win7 has this problem.. right?

Any help on the matter is appreciated
Thanks