It's amazing Fran Allyson didn't jump all over you.

The 1/4" phone jack is (supposedly) a balanced line-level input. If you plug a
mono plug into it, the plug's sleeve will short the jack's ring to ground.
This is normal; there's nothing inherently wrong with this. It's one way
unbalanced signals can be connected to balanced inputs.

http://www.behringer.com/EN/Products/B215.aspx

I suspect you have a problem that isn't really a problem.