I had this problem and I'd seen other people have it also... I was sure it was software and spent hours trying to backup (unsuccessfully), searching for a solution, wiping the device and finally re-installing the OS. In the end I got nowhere and the problem got progressively worse. In the end I took it to AT&T for a warranty swap, luckily they didn't give me a hard time about it.

Don't waste your time w/ this problem, whatever it is it F****S your BB up. Just swap it out right away.