[racket] v6.1 freeze on Windows: help needed

Several users have reported problems with Racket v6.1 on Windows where
DrRacket freezes. The reports have several details in common, I think:

 * When DrRacket freezes, it uses 0% CPU.

 * On machine where the problem happens, it happens consistently, and
   it doesn't take long after starting DrRacket.

 * No particular action within DrRacket is identified as a trigger, but
   in some cases, it might be related to switching the foreground
   window.

 * The previous release, v6.0.1, works fine on the same machine and
   configuration.

The Windows variant doesn't seem to matter; we've received reports for
64-bit Windows 7 and 32-bit Windows XP, at least.

Unfortunately, I haven't been able to provoke the freezing behavior on
any of the Windows machines/installations that I have tried (about 6 of
them, using various OS flavors, many different locations and ways of
installing, administrator vs. non-administrator accounts, etc.). I
think I must be missing a crucial ingredient --- maybe a particular
kind of network filesystem or a particular other piece of software.

If anyone else can provoke the freezing behavior, I'd appreciate
information about your configuration and observations. Most useful,
probably, would be a stack trace obtained by attaching Visual Studio to
the process when DrRacket is frozen. Otherwise, if DrRacket freezes on
some machines and not others, anything that you can say about the
difference in the machines could be helpful.

Thanks!