[plt-scheme] dr. scheme frustration

Hola, Scheme-people.  I tried installing Dr. Scheme 4.15 today on my 
WinXP SP II laptop.  Install went fine, language selection went fine 
(tried R5RS and Pretty Big).  But: insert cursor into either definitions 
area or interactions area - press any key - boom. "PLT Scheme GUI 
application has encountered a problem and needs to close." 

It's funny, I spent a bit of time with an extremely friendly developer 
on this list a couple of years back for exactly the same issue (I 
think), but to no avail.  I haven't tested each intervening release, but 
in rough terms I have to go back to 300 or so to find a version that 
doesn't bomb out instantly. 

Any clue how I might go about sorting this out?  Grazie!