I know I have been having trouble with offline lag, and a few others too there is a fix for this you need to disable Speech recognition and pre-load models, as this destroys your memory use and means UT2004 has to start caching to your hard drive, this thread is where I got the answer from after searching several.
http://www.ataricommunity.com/forums//showthread.php?s=&threadid=357772
This only affects offline play as far as I am aware, but if your not having any issues you may want to try it anyway to see if you can gain any fps or smoothness.
http://www.ataricommunity.com/forums//showthread.php?s=&threadid=357772
This only affects offline play as far as I am aware, but if your not having any issues you may want to try it anyway to see if you can gain any fps or smoothness.