Same here. Unit worked fine, upgraded to 3.50 and shortly after there is no sound in or out (digital, variax and USB work fine). Overall the unit works fine in terms of the screen and controls and has been well looked after. I've reluctantly had to purchase a replacement as I have gigs coming up which I need the Helix for. Trouble is I now have a non-working spare which seems a complete right-off. Line6 said they would likely need to replace the boards out of warranty which could cost around £500-£600 :(
Would really like to try downgrading the unit to see if that has any effect before I bin it.
