Over the past few days there has been a variety of user created content for the PS3 version of UT3, but unfortunately there is a range of reports that these are crashing PS3s.
Some are speculating that it is the fault of the Mutator mod released but there is s a bit of a 'problem' as it is not known as if Epic themselves will look into this issue as technically it is not their own content.
To quote from leukoplast: Well, seems the mods may have been all too premature. I was just playing campaign mode, nearly done with a level. As as it was counting down...boom the game freezes on me. So I restarted the PS3, started the game back up and the first thing to appear was this.
Sorry for the quality, but this was taken with my crappy camera off-screen. (click for bigger shot)
And for the record. I have downloaded and imported all the available PS3 mods to date. So not sure which one may be causing it.