Unreliable Playback / Out-of-sync?[solved]

Strange problem, just installed Cubase today…

When I start a track from the beginning, things eventually go out-of-sync. For example, I have a couple of synths that start off the track, when the drum beat kicks in about 15 seconds later it sounds slow and sluggish. Then everything appears choppy. But, if I start the track say at around 10 seconds, the rest of the track plays beautifully. That’s what I don’t understand. The other problem I’ve experienced is that the first midi note may or may not play when restarting the track. There’s just silence until the second bar comes in. The two problems appear to be related, but I’m not sure exactly where to start.

I wanted to add… it happens on export as well. Not good. Oddly, as mentioned before, when I export the track after the first 10 seconds on it comes out perfectly.

Appreciate any insights. Could it be ReWire? Something ain’t right.

3.40 gigahertz Intel Core i7-3770/multi-core
12GB DDR
Cubase 6.5 / Reason 6.5 using ReWire
Windows 7 Home Premium (64bit)
M-Audio Fast Track C400

This was an issue within Reason apparently, using ReWire. The “Play Focus” button on the Reason Hardware Interface was on… turning it off fixed the problem.