Hello,
Disconnect the scanner from USB and remove one of the batteries from the scanner. When you put the battery back in, do you see this message on the screen?
CPU SW Upgrade:
Waiting for USB
If so, the problem is the uP App in the scanner has been erased. You need to connect the scanner to a PC and use the RadioShack PRO-668 PC Application to do a CPU Firmware update.
73 Eric