[plt-scheme] teachpacks breaking in 4.2

I'm trying to install my tiles and sb-world teachpacks into 4.2.   
Both of them worked (alone or together) in 4.1.3, but when I add  
either or both of these teachpacks and hit "Run", I get a horrible  
error message:

require: namespace mismatch; reference (phase 0) to a module "C: 
\Program Files\PLT\collects\scheme\private\kw.ss" that is not  
available (phase level 0)

First, what's going on?
Second, how do I fix the teachpacks so they work with 4.2?  (And,  
preferably, with 4.1.x as well.)

I have to admit, I'm performing unnatural acts with a consenting  
"require", using it as an installer: when you "require" tiles.plt,  
it's supposed to install a file named tiles.ss into the local PLaneT  
cache, download and execute a file named install.ss, which writes a  
different file named tiles.ss into the installed-teachpacks directory  
that "require"s tiles.ss from PLaneT, which should be found in the  
local cache.  This was the easiest (for the user) way I could think  
of to add a teachpack into the list of available teachpacks while  
simultaneously adding its documentation to the Help Desk.  Anyway,  
this trick worked from 4.0 through 4.1.3, and it's not working now in  
4.2.


Stephen Bloch
sbloch at adelphi.edu