oh boy...
OK, in the mixer window, just to the right of the master volume control, there is a little dot thingy. When you click on it, it goes from stereo to mono. It's really hard to see the differences in the graphics. It's like two circles next to one another means STEREO and one solid circle means MONO. Again, it's really hard to see the differences, but go ahead a click. Tell me if that fixes your problem.
Cary