Flash updates can sometimes be problematic.  Often a reflash will fix it. Sometimes you have to roll back to a previous flash version first and then re-apply the latest flash and that will fix it.

I suggest you try rolling back to 1.71 first and see if the JTV works normally again.  If it does then try the 1.82 one more time.  If it fails again then its your call - report to Line6 and see what they suggest (they may need you to send it in for fixing) OR roll back to 1.71 if you don't need or want the improvements with 1.82 and at least then you have a working JTV.

Hope that helps.

Best Regards

Eddie

How are you guys listening to the guitars? Are you running through VDI to a POD, in which case there could be other issues or multiple signals coming through (Vax + mags)? Or is it isolated to just guitar -> amp via normal guitar lead?