This is something I've struggled with in Oblivion and Fallout 3 too.

I have a great graphics card, and and these three games run really well. Too well. The FPS is frequently in the hundreds if v-sync is off. But if I leave v-sync ON, I get atrocious mouse lag that makes me feel like I'm controlling the mouse with an anolog stick.

And turning v-sync off is broken too... just turning it off doesn't do anything, you have to go into the .ini file and change iPresentInterval from 1 to 0. Then (and after fixing the mouse acceleration glitch too) my mouse works perfectly. But the game still runs at over a hundred frames per second.

In most games this wouldn't be too much of a problem. However, this causes the game to SPEED UP. Lip syncing becomes messed up, and I run like that guy with the bunny hat from Ocarina of Time.

iFPSClamp doesn't do anything either. It's currently set to 0, and if I set it to anything higher, like 30, 55, or 60, it will strangely cause my FPS to shoot up to the thousands on the menu screen when it was previously in the hundreds, and it makes me run EVEN faster in the game.

In Oblivion and F3, I finally fixed this problem by limiting the FPS with the great mods Oblivion Stutter Remover and Fallout Stutter Remover, which allowed me to limit my FPS without enabling v-sync. This is my goal.

However, New Vegas Stutter Remover seems to be broken. So I really need a solution to this ridiculous Gamebryo bug.

Oh, and I also tried that FPS limiter program online. Worked for Fallout 3, but not New Vegas for some reason. But it didn't work with the script extenders for both games, so that's out of the question.

Thanks for reading this giant rant on the biggest problem I've faced with these three otherwise fantastic games.