Hi jbp006,
Have you tried turning the mini-jack around in the port? That works for my system sometimes.
Also, check in Volume Control (double click on speaker icon by clock) to see if the Balance control is centered.
If you have access to another computer, try your speakers on it to see if the speakers are at fault. Likewise, you can try the other speakers on your system and see if you encounter the same thing. Will help you to identify exactly which component is at fault.

Cricket