HELP !! My AVR300's lost it's voice

[Shaka]

H E L P !!!

I was watching a DVD this afternoon when an hour or so into it the sound died on me and I haven't been able to get it back. I tried various surround modes and can't get any sound. I've also unplugged everything and plugged it all back in, turned it off for 10 mins etc etc. After a few hours of trying everything I can think of, this is what I can get:
I can only get sound from analogue sources but in "Direct" stereo only. This applies to CDs, TV and tuner. If I switch to a surround mode for either digital or analogue signals, I just get sort fluctuating humming noise. When I switch between different inputs I get a loud crackle and then that horrible low humming sound which goes up and down.
I've been through the menus and all the settings are exactly as they were. And there is no test tone either, just that humming sound again. It's very strange as I can play my CDs (via the DAC connected to the CD inputs on the AVR300) and there is perfect sound (only in stereo "Direct" though) with even the sub being engaged.
PLEASE HELP !! What has happened to my surround sound?

[Shaka]

Ok, after further investigation I think the problem might be linked to the software. I just checked the software version and it displayed s/w version at 2.90, but for DSP it said "N/A".
I tried updating the DSP s/w (after lugging the PC all the way downstairs). After pressing RDS + Down it states "Update Req?" (as expected), but when I press OK, it says "pls wait ..." and then says "update error ...".
I then ran the main s/w update which ran ok. After rebooting the amp, I checked the s/w version again and this time it DID display DSP 1.12, but I still get no sound in surround modes. I tried updating the DSP s/w again byt still get "update err ...".
Do you think something has blown in the amp? Very surprising as this is a new replacement (a few weeks old) and only gets used for a few hours per evening at reasonable volume levels (60-70 db)

[Crustyloafer]

Sounds pretty serious, best get it back to Arcam for a healthcheck.

[Shaka]

Well I got another replacement AVR300 yesterday - the third one. Top marks to Sevenoaks(P'boro) and Arcam for a speedy hasslefree service.
I'm a bit concerned, however. When I got the unit out of the box and plugged it in, I immediately checked the S/W version and it was 2.84 as I expected because the previous one was the same out of the box. The DSP version, however, came up as "DSP N/A" .... This is worrying as the unit is brand new straight from the factory. This msg was also displayed on the unit I returned after the fault developed. I performed a software update and it now states "SP 1.12", the main s/w took 4 attempts before that finally updated to 2.90.
My worry is that is this unit going to die on me within 3/4 weeks as the previous one did? I can't return it because it is working fine at the moment, but I'm very concerned and very surprised as Arcam have a great reputation for their quality products. But this is the 3rd unit ...
Any comments.advice would be appreciated, especially from Arcam. (Where are you John/Andy??)