Currently Being ModeratedAug 24, 2010 4:34 PM (in response to clemmert)RE: M9, Input jack shorting out.
That happened on my personal unit. It turned out to be a loose solder joint past the input jack connection point.
If you're still within the first year of new product purchase, I recommend making a copy of your purchase receipt and getting the M9 to the nearest Authorized Line 6 Service Center in your area: http://line6.com/support/serviceCenters/
The tech(s) can check out the input jack and solder joints no charge to you and correct the issue without voiding your warrnty.