As NISA Game support told me...
"Suck it up, 'cuz nor the programmer nor will we fix these freezes, 'cuz it entails too much reprogramming".
These are the foolproof ways of game lockup (it doesn't matter jack what firmware you are on):
1. Post your rank online, get Error 0000000 and try to repost right away. Freeze.
2. Enter status/equip screen and cycle quickly through the characters. Freeze.
3. Enter the gallery on any image, hit square to get rid of the caption and cycle through images quickly. Freeze.
4. Rizelea's path chapter change from 9 to 10, if you don't skip it. 1 out of 3 times it will freeze.
5. Enter the black market and change your points into more than 10 different items. The game will either freeze completely or do it for more than one minute.
6. Enter status screen and press down to see a list of equipped meteorites, then cycle through characters quickly. The worst freeze. (CAUTION: This freeze is THE worst... Using the PS3's front power button will do squat... You will have to physically turn it off by using the back power switch, which also risks damaging your PS3's harddisk. Attempt it at your own risk).
There are more, but the whole lot of them can be summed up to something NISA's game support told me in their email response: (quote)
For many of those [the lockups/freezes], think of it like this: when you try to open all of the programs at once on your computer, what happens? It'll slow down and eventually lock. That's the premise behind the issues with how TriUni was programmed. By cycling through menus or images quickly, the disc is being forced to read them all at once. There's no need to rush! (end quote)
Basically they told me (and by extension all of us having issues with the game) to stop whining and to resign to having bought a fatally faulty game.