frankie123dd,
What model Xperia do you have?
I just tried a factory reset. Still no good.
I also tried swapping SIM's thinking the hotspot/tether provisioning from AT&T somehow got messed up. That did not work either.
Devices can connect to the hotspot, but cannot get out to the internet.
I'm going to try re-flash back to Gingerbread, test that and work my way back up to ICS 4.0.4
Regards,
Bob H