I recently purchased a 2GB MicroSD card. I have loaded some files on it, but every time I insert the card, my Pearl works great for about 5 minutes, then locks completely. it goes unresponsive. I pull the battery and the same thing happens. I pulled the battery again, took out the card, and the Pearl works completely fine again. I don't think it's the card because (with the adapter), my computer recognizes the card and transfers files perfectly through my Media Card Reader.
it is whats on the card, i had the same thing, really look at the files on the card, re format the card as well, that is what i did, first saved all the info off card to computer then format card and then reload info and such back on card, this will likely help your situation, it did mine. I even took my phone back once and returned when i did not know what it was. Try that and let me know if it helped.