Hi All.. well been using Sonar for years..and all of a sudden I get the silent buss notification..now usually I can go into Options..Audio and select my presonus firebox driver...but its not there....it is there as midi..and selected for it. I reenstalled sonar and firebox with not change...can you help? Thanks David

Well its sounds like Sonar or your computer is definitely not seeing the Firebox.

Does it show up as a device when you Right Click on the Speaker Icon as a Playback/Record Device?

Maybe but hope the Firebox didn't crap out on ya.  Maybe Unplug and replug both ends on its cables as well just to make sure the connection is good.

When you say you reinstalled the firebox,  it did reinstall the most current driver for it?

Yes Mike. I insalled the latest driver(: I know the firebox is working..blue light comes on to indicate midi working and sonar sees it as midi when I select midi divers but just not audio in options so everything is sent to silent buss and asks to select drivers which there is no way to select firebox because its not a choice nothing is there to choose.. gotta be something in my computer settings

thanks mike yes i have it available on the computer when right clicking on speaker icon it shows up

ASIO driver mode? 
Is the Firebox the only audio interface selected? 
Check Windows Device Manager to see if its listed as an audio device. If not, try replugging the cable. FW cables can be a little finicky.