Trouble installing MrSpidey

[Mark Guzdial <guzdial@cc.gatech.edu>]

I just tried to install MrSpidey on my Mac, and I got these error 
messages, which I can't understand.  Suggestions?
...

setup-plt: Making .zos for MrSpidey at Guz 
G4:Applications:plt:collects:mrspidey
make: Failed to make :compiled:drspidey.zo; compound-unit/sig: 
signature "setup:plt-installer^" not defined in: (compound-unit/sig 
(import (framework...
setup-plt: Making .zos for MrSpidey Sba at Guz 
G4:Applications:plt:collects:mrspidey:Sba
setup-plt: Making .zos for MrSpidey Gui at Guz 
G4:Applications:plt:collects:mrspidey:Gui
setup-plt: Making .zos for MrSpidey Tool at Guz 
G4:Applications:plt:collects:drscheme:tools:analysis
setup-plt: Done setting up
setup-plt:
setup-plt:  Error during Making .zos for MrSpidey (Guz 
G4:Applications:plt:collects:mrspidey)
setup-plt:   make: Failed to make :compiled:drspidey.zo; 
compound-unit/sig: signature "setup:plt-installer^" not defined in: 
(compound-unit/sig (import (framework...
call-with-output-file: cannot open output file: "Guz 
G4:Applications:plt:collects:setup:errors" (errno=?)

--------------------------
Mark Guzdial : Georgia Tech : College of Computing : Atlanta, GA 30332-0280
Associate Professor - Learning Sciences & Technologies.
Collaborative Software Lab - http://coweb.cc.gatech.edu/csl/
(404) 894-5618 : Fax (404) 894-0673 : guzdial@cc.gatech.edu
http://www.cc.gatech.edu/gvu/people/Faculty/Mark.Guzdial.html