I have a '92 300TE 4matic with the following problem:
recently after disconnecting the car battery for another job, my radio started to flash "CODE" instead of working when i turned it on.

I obtain the code from my local dealership, inputed it but then the radio flashed "WAIT" for about one week and then again began flashing "CODE". At no time did the radio worked.

The dealership said i should re-input the code. This I did; the radio screen went blank and now the radio does nothing. Now when I turn it on, the screen is blank, the power antenna goes up for about 5 mins and then goes down.
Nothing else happens.
When the antenna is up, pressing to the power button which would normally turn off the radio and bring the antenna down does nothing.

I went back to the dealer, they verified the code as being correct for the radio but are saying that the radio is nonfunctional (i.e. broken/unfixable) and that i need a new radio.
Prior to all of this the radio was working fine.
Any ideas/suggestion?
Had any one seen anything similiar?