monticello gets keyNotFound for class on reload?

When loading some Monticello packages (e.g., VRML in the hedgehog  
contrib repository, and some of my own), I get a key not found error  
within MCClassDefinition>>createClass. This always happens when  
Monticello decides that a "reload" is necessary.

What's up with that?

This does not happen with the version of Monticello that was in the  
SDK beta (-ar.288), but only with the newer versions that are there  
now. (I think the older MC does not try to reload, FWIW.)

-H