Allright, I've seen that this is a common issue with both NV and Fallout 3. Anyway, I have trouble with mouse lag, it feels exactly as the mouse lag you usually get when vertical sync is turned on in other games. Except vsync is turned off both in the game and in CCC.
Oh, and i'm using a HD5970 card. This is really annoying, I stopped playing the game when it was recently released because it had so many buggs. Now I thought I might give it a try, then this [censored] happens... Please for the love of god help me! =)

I tried changeing iPresentinterval=1 to 0 and it fixed the mouse lag. However it seems as the game is running way faster then it ought to. How do I fix that?

http://shortgamer.blogspot.com/2010/10/hint-mouse-lag-in-fallout-new-vegas.html

"add

fForegroundMouseAccelBase=0
fForegroundMouseAccelTop=0
fForegroundMouseBase=0
fForegroundMouseMult=0

at a certain point in two .ini-files. The first file is located in the F:NV-folder and it's called Fallout_default.ini. You have to search for the [Controls] part in the .ini and then just copy-paste the above lines at the end of that block.
The second .ini you have to change is located in your My Games directory. Somewhere like C:\Users\
I haven't tried this my self. I am not familar with iPresentinterval, which seems to have unexpected consequences.

I've already tried that. However I only added those lines to the Fallout_default.ini but it seemed to remove the acceleration anyway.

The delay on the other hand was still there, so this didn't work for me

Tried putting it into both .ini files and it made no difference. I also tried to download the ATI Tray Tools or whatever to adjust my Flip Queue, and that didn't work either.

I know for sure that this is a vertical sync problem because i always have 60fps, question is, how do i fix/work around this issue?

Please help, Im starting to regret even owning a PC these days...