I've only had my phone 2 months but I have had 4 different SD cards in it. Becasue of my excessive synch testing I have moved several GBs of pix and music back and forth from then several times without issue. Granted it's only been a couple months so it's not a greeat baseline. I will tell you though that recently I went to AMAZON to buy an SD card and even after great reviews, when I went to add it to the cart I got a warning that said something like
"Many of our users reported issues with this item. it is temporarily unavailable until we can determine if we have problems with our inventory or the manufacturer".
So there may be issues with the cards too. I would suggest bringing the phone in and let them deal with it.