I'm finding this too. I contacted Access support, and was told I'd be invoiced for a new output board if that would fix it - no invoice, no output board, and more to the point no answer on whether the output board would be the issue here.
Volume turned above halfway, I start to get distortion on the left channel (analogue output 2) - not present on SPDIF, USB or Sub outputs, only on the analogue output 2. It's not present on headphones, which is interesting because surely the volume control affects the headphones too - of course this makes me really suspect the output board more, but I'd like to know for sure before going nuts trying to get the replacement part.
Of course if the headphone output is on a different volume circuit somehow, that makes it EVEN MORE CONFUSING, but this isn't the first Virus I've had with this behaviour - I just assumed they weren't all they were cracked up to be and moved on.