call at&t there customer support should be more helpful

Hey, I have a AT&T issued 5600 and I am using Cingular. I had the phone unlocked and everything but the other day I was playing some pool game on my phone and the phone froze, so I'm like whatever. I go to take the battery out and put it back in. I start up my phone and it gets passed the Audiovox screen but it stays at the Windows Mobile screen. I tried the hard lock combo, the 2 soft keys + power button one. I get into the press 0 screen and I press 0 but it still hangs at that Windows Mobile screen. Anyone have any advice or maybe this is a known problem? Thanks!