I thought your data was saved online? im pretty sure this happened to me once and i just started a new save and i kept my rank, weapon's etc etc.

If you're playing single player in BF3, you're doing it wrong. It's horrid. Anyhoo, that happens to me every bloody time I turn the game on. Cloud and HDD are both corrupted. Just set up your classes and they should stay the way you want them. You will have to change your controls and server filter every time, unfortunately.