Okay I figured out the cause of my playback pause!
On a whim, I changed my audio driver from the default WDM/KS to ASIO and did a Wave Profile...
BOOM! INSTANTANEOUS PLAYBACK! I seem to have two Softsynth tracks in my project, both VSTis, so wonder if that is a factor. I haven't played anything back with straight audio tracks running under WDM/KS though.
Which type of audio driver is everyone here using, WDM or ASIO?
I kinda like how you can adjust the latency on WDM whereas it's more of a fixed deal with ASIO. But if ASIO is the way to go these days, then I gotta get used to it.