I know this is an old thread, but I thought I would answer for anyone that end up here in the future.

For games on Unreal Engine 3 like this one, I would recommend disabling in game vsync through the config files and using the Nvidia or AMD control panel to turn it on. This will allow higher frame rates and also fix stuttering issues.

Open the main game folder on your computer and you should see 2 folders called "Engine" and "UDKGame". Open the folders Engine, then Config and there will be a config file called BaseEngine. Open that file in a text editor and search the file for the word "smooth".

You will find a setting called "bSmoothFrameRate=". Set this to false. This may show up in more than one place in the file, so you will need to set it and then search the file again and set any you find to false.

Then go back to the main game folder and open UDKGame, then Config, and look for the file UDKEngine. Search this file for the same setting and set it to false.

Now that vsync is disabled from within the game, use your Nvidia or AMD control panel settings to force vsync on for this specific game.

You could also just leave vsync off and get as many frames as you can or use other software to cap the frame rate.

There are other settings within those config files to control what frame rate the game will run at, but they don't seem to work in some games. I have been able to adjust them in other games, but I could not get them to work in this game. They should be the next 2 settings after the one I mentioned above.

bSmoothFrameRate=FALSE
MinSmoothedFrameRate=22
MaxSmoothedFrameRate=62