I am experience a difference in the output of tracks vs main.  I am soloing a bass guitar, RMS about -6 DB with the fader set to 0 db..  However the mains are staying in the red with the fader at 0 db, also RMS.  The bass track is not assigned to any sends- just straight to the mains.  Obviously I can turned down the mains, but is there something incorrect in my setup that could be causing this?  Perhaps something to do with my audio interface?  What to check and how to fix?
 
Any help appreciated.
 
Windows 7, Sonar X3d, Maudio Fast Track Ultra.

There is no way your mains are at 0dB RMS. You have it set to peak, not RMS. 0dB RMS would sounds like poop on stick being ran over by another poop on stick. There is no way your track is at -6dB RMs. These is just too hot. 
 
Your total mix shoudl be between -14dB RMS to - 9dB RMS. Im pretty sure your getting confused over RMS ansd peak dB values
 
CJ

Thanks for the help.