UPDATE AUGUST 28 2007:
Hey, thanks for replying. For a while it seemed no one was gonna help me out. Anyway, here's more food for thought...

I took my mobile to the dealer for service again, but this time I went straight to the service centre (rather than send it in via shop I bought it from). Guess what? It took them 10 minutes to repair it this time. 10 minutes!! As opposed to the whole week I waited last time. Anyway, they flashed my phone again, apparently...

But guess what else...

It's busted again! YAY! WSOD for the third time. And this time I was very careful not to bring my phone anywhere near my memory card! The guys at the service centre told me I (probably) had a virus in the memory card, though when I asked them to check it themselves they said they couldn't. Anyway, this time all it took for the phone to die were two pictures saved to phone memory. The first one took around 3 minutes to save, but got saved in the end. The second one took more than 10 minutes, then the phone became unresponsive, then VOILA! WSOD. And no, the phone memory was nowhere near full, as I didn't put anything inside anyway. Now I have three theories, and I'm hoping you guys can pitch in here:

1. The phone memory is corrupted or damaged, due to overheating or internal component failure or something like that. As a result, anytime I try to write to phone memory (e.g. saving pic to memory) it wipes everything out.
2. There really was a virus on my memory card, which somehow spread into my phone memory and somehow damaged it so bad that even after flashing the phone memory can't handle anything. Has anyone heard of a virus that attacks sony ericsson phones? Correct me if I'm wrong, but viruses attack only Windows mobile and Symbian phones, right?
3. The only other thing I did (other than take that pic) was download my contacts from the sim card to the phone. Could this be a cause of WSOD? Has anyone experienced something like this before?

Once again, I'd appreciate any and all help!