[plt-scheme] Frequent Dr. Scheme Error

Hi All --

Recently, Dr. Scheme has been crashing on me a lot. I'm running it on a Mac,
using HtDP Advanced Student Teaching Langauge, and usually generate the
error after Running the "Check Syntax" function.  This only started
happening after I installed the PLAI software.

Here's the error message ---

sequence-contract-violation: negative: method change-style cannot be called,
except in states (unlocked), args #(struct:object:style% ...) 7226 7245 #f

 === context ===
/Volumes/PLT Scheme v4.2.5/PLT Scheme
v4.2.5/collects/drscheme/syncheck.ss:1877:32
/Volumes/PLT Scheme v4.2.5/PLT Scheme
v4.2.5/collects/scheme/private/map.ss:45:11: for-each
/Volumes/PLT Scheme v4.2.5/PLT Scheme
v4.2.5/collects/scheme/private/map.ss:45:11: for-each
/Volumes/PLT Scheme v4.2.5/PLT Scheme
v4.2.5/collects/drscheme/syncheck.ss:1817:4: annotate-variables
/Volumes/PLT Scheme v4.2.5/PLT Scheme
v4.2.5/collects/drscheme/syncheck.ss:1245:38
/Volumes/PLT Scheme v4.2.5/PLT Scheme
v4.2.5/collects/drscheme/syncheck.ss:1242:35

Any suggestions?

Thanks!
Dave Yrueta
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.racket-lang.org/users/archive/attachments/20100426/81ed4003/attachment.html>