silly question:
now that your tone pots act like volume pots, do your volume pots act like tone pots?
Just thinking something through.
I'll try switching caps and see what happends.I just asked a similar question here. It seems that the simple answer is that your capacitor is being bypassed somehow, either due to a short around it, or because the cap itself has simply stopped working. I'd check the cap's condition first of all, and look for incorrect wiring or poor solder joints.
I'll try switching caps and see what happens.