plugins/ instrument tracks lost sound?

[bifbangpow]

So I'm sitting here composing, and in the middle of using my Play plugin, i suddenly lose playback sound. It registers a signal when I trigger it with my midi keyboard, but I hear nothing.
I tried other plugins as well... xpand, mini grand, structure... all doing the same thing.
The track is going to the right output and actualy playback on other audio tracks play fine. I just cant seem to hear anything when I'm using an "instrument" track plugin.

please help.

pt 11.3
mbox pro 3
windows 7
hp zbook 15