There are various posts on the official UT3 forums saying that one of the user created mods 'Cooked' by Epic games is crashing PS3's.
People are pointing towards the 'Mutator' mod that was released.
As this is a user mod it is unclear who will look into this problem as if Epic look into the problems they will simply be a free testing arm for PS3 user mods and this task will become impossible once they release their utility for pc users to cook mods themselves.
This mod was obviously cooked for use by Epic so i think they will look into it but it does raise some questions about managing user created mods being used unintentionally/intentionally in virus like ways.
Just like mods on pc do not install multiple ones at a time, test it fully after installing it. At least then you know which mod caused the issue and it can then be removed.