Need for Speed 'speeding' too much! (NFSU and NFSU2)

hello guys, i'm facing a strange problem with nfsu and nfsu2, no matter resolution and depth and graphics options (usually everything ON) the game seems to speed up by 500ms or two, like playing a movie in fast forward, even putting the game in like 1280x1024 with everything on makes it run nicely and fast, locked on 60fps but on random moments i feel the game playing on 'fast forward' for 500ms or 1 seconds then comes back to normal.....happens more when car in high speed, anyone has a clue of what can it be?

ps : in this computer i also have The Sims2 and Doom3 , both run FINE, the sims2 runs at 1280x1024 with everything on and normal play speed, as doom3 , no random speedups

system:

Gigabyte K8N-SLI
ASUS Geforce 7600GT 256mb
AMD Athlon64 X2 3800+
1GB DDR400 Samsung
300gb ide hd [maxtor]
Windows XP Pro -32bit- (service pack 2 installed, drivers from NVIDIA directly (no asus drivers or those crap)

thanks

Hey, man.

I might be wrong, but I think that you have "Motion Blur" enabled in the graphic options section of the game.
This makes things not so clear to see when you reach a certain speed, or acceleration (NOS usage).

Just disable the option if I don't like it. (I surely don't like it).

If it's not this, I have no clue what could be wrong.