When I try to load
http://modules.squeakfoundation.org/People/dvf/Packages/SMBase-dvf.13.mc
z into a more or less clean image 3.7 using MC, I get an error because
of adding a variable to a class that exists in a superclass (IIUC). I'd
guess what is happening is that the superclass gets redefined to not
have the variable, but it comes later in the load order. This can be
worked around by proceeding in the walkback. After that I loaded the
file again, and things seemed ok. 

Found this while trying to create a load script for an SM2 alpha
version.

Daniel