Buzzing sound on audio mix down with m-audio project mix i/o

Im having trouble with mixing down an audio sample with mutiple vsts in cubase 6.05

Im using a firewire m audio project mix as my soundcard and just before it wasnt mixing down with a buzz and now it is. I dont have any plugins besides a mastering one on my output.

anyone else have this problem? could it be my mixer console?

Without knowing what “your mixer console” is or how you have anything connected?

Mysterious buzzing sounds are commonly due to bad earthing or ground loops?

Or having certain bits of gear stacked too close to each other!