Has anyone else had problems using multiple heat power loads w/temp controller curves in a thermal study?

I have a a study on a simple assy with three heat power loads, one simulating a transistor and the other two resistors, all with temp controller curves.

I can get the transistor load w/temp controller curve to work with each of the resistors loads w/temp controller curves independantly, but not all three together.

In addition, if I turn off the transistor loads temp controller curve and turn on the two resistors temp controller curves the study does not solve.

I've also tryed combining the two resistor heat power loads into one with a single curve with the transistor curve on, but this didn't work either. 

Each is on a independant surface with it's own temp controller curve, but the solver stalls out and doesn't solve if all three are active.

I've rebuilt the entire assy and study from scratch to make sure I didn't miss something, and it's still not working.

Anyone have any tricks to try?

Thanks Glen