Sonar PRO suddenly not recording audio

Hello All,
 
I've been using Sonar Professional for a couple of years, have never had any really issues.  However, suddenly (and I mean suddenly...within the same recording session) it won't record audio to specified tracks.
 
I've trouble-shot all connections, settings (drivers, recording preferences, my Audiobox USB interface...everything!), and all parameters and hardware are set EXACTLY as they always have been.  The track that I'm trying to record to (and I've tried - and had the same issue - to record Bass, vocals, guitar) highlights, it shows as armed, and I'm even getting input levels from the instrument or mic.  However, when I actually hit "Record", although the track lights up red as usual, nothing shows up in the track, and nothing is recorded/saved.
 
Literally, I was recording guitar (using two Apex-180 pencil condenser mics, in stereo) without any issues, switched over to bass (direct line into my Audiobox USB on channel 1), and...nothing!  Tried bass in both channels on my Audiobox, as well as Apex-435 med. diaphragn condenser mic for vocals in both channels...same problem.  Sonar PRO recognizes the input signal, it just won't put the input "down" on the track.
 
HELP!  (and thanks in advance!!)
 
James