Session Drums 2 don't output to audio when SMPTE syncing

This pretty much says it all: Session Drums 2 don't output to audio when SMPTE syncing.

After many hours trying to get SD2 to work and finally getting there, I decided to try and replace some drum sounds I had previously recorded on my KORG D1600. Everything syncs fine, but when SONAR chases, the sequenced SD2 drum sounds don't output from my sound card to the KORG.

I can even manually play along on the channel that's got the session drums, and the output is fine.

Anybody know what's up?

TIA,

popmidi