Samsung DSR9500 VIA CI volume problems

Hi folks,

my 9500 of around 18 months has developed a strange 'fault'.

Seems that I have lost control of the volume setting. The on scrren volume bar stays at 100% (fully to the right) no matter what I do. If I power cycle the unit audio is present but as soon as I try and change volume up or down the audio cuts out but the volume bar remains at 100%.
This problem is apparent whether I use the remote or the front panel control.

Stuff I have tried so far:
1. power cycles
2. reset to factory defaults
3. reload of firmware (emu 4.8)

no joy.

Anyone seen this before and/or have some ideas ?

Unit is usable as long as I don't touch the volume controls after power up.