ThingLab Won't Filein

I am trying to use the ThingLab but I cannot get past installing it. I downloaded ThingLab v2 today. I am running Squeak 3.2.7 beta 6 (Carbon) updated to 4956 under Mac OS X 10.2.1 on an iMac. I open a new MVC project and file in the Predefs.cs without any trouble at all. As soon as I try to file in the other part, I get the message:

     "You may not create any more undefined objects - use nil."


Any suggestions? Thanks!

-Mark