VST patches reset after unfreeze

I'm running a large project (53+ tracks and 15+ VST's).  I'm now in the mixing phase of my project and consequently froze many VST's in order to save some CPU cycles.  

When I unfreeze some of the VST's (e.g. Dimension Pro, Session Drummer and Reaktor), the patch that I had assigned to that VST goes back to the default patch.  This is a pain because some of the sounds that I had chosen on the VST's are obscure and hard to find patches.  So it is very time consuming to go back and find patches, tweak track, freeze again, etc.

BTW, on another small project, this doesn't seem to occur.

Is anyone else encountering this issue?  How can I ensure that upon unfreezing of a track the VST's chosen path/present stays?