I have had the same problem with my Behold 2 and I think I may have figured out the problem (Tmo and Samsung where useless) I am on my second phone and second memory card. The same issues keeps happening. I have pics and music on the SD card... I get a message that the SD card is blank and I should format it, then I lose everything on the card. In my case, I noticed the issue happened again after downloading some pics to my computer. I think it is because of the way I hooked up and unhooked the phone from the computer. When you connect the phone to the computer the phone prompts you to "mount" the phone and when you are done, you can it "turn it off" through the phone but...you have to "eject" the device from the computer first, then turn it off through the phone and then unhook the usb cord. It corrupts the files on the card in the phone if you don't turn it off from the phone and the computer before disconnecting it.
I just did it and I have had no problem so far. I will let you know if that changes but i hope that helps someone having the same problem.
I just did it and I have had no problem so far. I will let you know if that changes but i hope that helps someone having the same problem.