I've experienced the exact same problem as this fellow here: http://line6.com/community/thread/62979
"500$ isn't chump change to most of us working stiffs and I feel this needs to be treated with some extra care. Your customers deserve better than accusatory responses that basically end up calling them idiots."
I am sorry if you are upset but if your M13 is experiencing the issues listed in the thread it needs to be taken to an authorized service center for repair:
Line 6 Customer Support