FWIW... reset does not help, re-register with network does not help, power off or pull battery does not help. Deleting re-adding user to BES does not help.
Send a message from the device - and messages come flying in that have been queued up. Im not sure the bahavior is constant, rather it seems to 'go to sleep' periodically for lack of a better phrase. For a while (hour? 2?), everything works great - and then it stoipps again.
ATT Wireless has been no help whatever, and RIM will only refer us back to ATT.
We have a handful of other blackberries that do not behave this way. (Mostly 957s, and a couple others - most with other carriers). This device is a 7280 which replaced the 7210 - in a desperate attempt to fix it ($350 on top of $499). We also have a 6510 from Tmonile which seems to work dandy.