Have you checked the transaction history to make sure it wasn't sent out or stolen? I had a near heart attack when I forgot I transferred some coin to another address once upon a time.
Yes, checked "last operation" (or is there any other way to see the transaction history?), I believe that is what it was called, and there were no transactions there.
Very strange...
I don't think it was stolen as the other coins, in the other wallets, are still there.