I was playing PoR w/ 1.0.2. It would freeze (at most times, at the warp points and wandering around the menu). As long as I was fast, the freezing could be avoided. When 1.1.0 came out, I had my old 1.0.2-based save file. The save had 1000% of the map explored, most items collected. I state this because one underlying factor has been that the more you discover, the easier it is to freeze up.
Here's the oddity. I loaded PoR back onto my DS-Xtreme after the 1.1.0 update and then transfered my save from back on 1.0.2. It would not freeze up no matter what I tried. I could hang in the warp map forever. Rapidly changing from the game to the menu did not cause a single lock-up. I could scan every single item, monster, etc. in the menu lists. I even started new games under various modes, and upon reaching areas where freezing should have happened, it did not.
Your guess is as good as mine as to why some units seem to be able to play Portrait of Ruin, while others cannot. Perhaps, Team DS-X will figure it out. Just don't expect them to speak publically about it, as they're quite stern about their rules of zero conversations of commercial software.