dl4 volume problem

["Xavier WATKINS" <xwatkins@wanadoo.fr>]

Hi,
I've had a line dl4 for abut a year, and been quite happy with it so
far...since about two weeks ago, I plugged a mic in the second input along
with my guitar still in the first. That shouldn't cause any problem
though...???
Basically what happens is that when I record a loop, it now plays very very
low (almost silent) and the problem is fixed if I plugin something in the
second input when recording!!! Did any one went through something like 
that?
(tried resetting and enabling/disabling bypass, but didn't make any 
change).
Many thanks