I caught Beldum today, god damn hard to catch it!!!! Then I tried to purify it follow the hints Kithros said.
I think the trick to purify beldum is, you must maxed out the tempo of all 9 purification chambers, then you would be able to purify your beldum. I dont have 36 normal type, so I have to play around with the typing with those pokemon I caught to max out all 9 chambers. An easier way to do that is, caught 36 normal type pokemon (have to be just normal with no other type), and fill them in all of your chambers.
p.s. I am not sure is that the original (or right) way to purify Beldum, this could be a bug like Kithros say. Only Jan knows.
I saved in the PC of that Alien lab town in V6, open the game in V5, get in the Alien lab, saved before entering the final room. Open V6 again and get into the final room, get the card pieces I need and leave.
Nothing crash or went wrong at all. If you save in those map that are the same in both V5 and V6, then open your save in V5, it should not freeze or go wrong.
Anyway, back up your save before you do that, then the risk is pretty low I would say.