Hi John / azslow3,
The freezes seem to be more MackieControl / X-Touch related than Slate. When I unplug the X-Touch the trouble goes away.
 
I should clarify that when it freezes its right at the point you expect the project to become visible in Sonar and the X-Touch faders move into place. So what actually happens is you'll see the mouse cursor spin and also see a spinning 'W' for my waves plugins. Then the mouse stops spinning and the project never becomes visible, nor do the faders move.. Sonar is then frozen. If I unplug the X-Touch everything works OK...even with tons of Slate plugins.
 
I started using my MacBook Pro as my permanent DAW this year, even though I've had it a long time. I also bought the X-Touch this year and shortly after I noticed the freezing. On my old computer I used a BCF2000, Sonar 8.5 and WinXP.
 
I'll try removing all my Slate plugins to see if there's any change. But it seems to be something related to MackieControl / X-Touch.