[MrGoodCat]

i had an issue with a 4gb card when i first got the phone, installed one cab off it, then it wouldn't work. i'd reset and it would show up in file explorer but as soon as i tried to use it would disappear. turned out to be the card. i am now using my 1gb that i have had for ages and it works great.

ps i believe there is a thread here somewhere that deals with specifically 16gb class 6 cards, that could shed some more light on your specific case.