Message ''--ILLEGAL'' appears on VFD and no channels are displayed

The unit is fairly new, used very little and has worked correctly. Suddenly it started giving the message ''--ILLEGAL-'' on the VFD and no pictures are displayed. When scanning for channels, it can't pick anything up (signal &quality at zero). I know my dish setup is fine by using it on anotherreceiver. All other functions seem to work normally (eg I can play back previously recorded material from an external HDD and change settings from the main menu). I have no problem updating the firmware, but to no avail (I've tried the last three versions from the Fortec website).
I would appreciate any ideas. Thanks in advance.

Des