From Gaming Bits:
"Day one of Unreal Tournament III for the PS3 isn't without a few bumps. One of the more significant bumps is one of the most touted features of UT3 on the PS3: support of mods. Epic Games is aware of a few problems that popped up in the first day of Unreal Tournament III on the PlayStation 3.
So it looks like there is some refining to do. Remember the game was pushed up to make a December 2007 release instead of January 2008. So we inevitably face glitches. The good news is Epic is listening and working on the issues. I did experience the same issues with voice chat. Multiplayer gameplay last night was smooth. This morning it was significantly laggy. We'll keep you posted on any updates or when a patch is coming."
Planet Unreal has posted on the issues.