I'm having a related problem. Built the latest PowerPlant and Constructor code from sourceforge as Universal Binary in Xcode 2.4.1 (running on OSX 10.4.10 on a MacBookPro), ran Constructor, but two problems:
(1) The Catalog window is missing subclasses (e.g., in the Panes tab it shows LPane, but none of the descendant classes).
(2) Can't edit *.PPob files, they are dimmed in the "Open: Constructor File" dialog that comes up with File | Open Project File...
Tried mucking through the CLWindow and CLDisplayClassTable code in debug, nothing definite yet but nagging suspicion that the problem is upstream, perhaps in reanimating classes? Anyone else seeing this problem? Any ideas on a fix?