I can't reproduce this on Linux.  However, I've seen an informal report of something like this happening before.  It looks a lot like something threading related, but I don't see any threads in what you're doing.  (Though I don't know the details of how the profile module works, on either Linux or Windows.)

The use of locals() in the Context constructor is an unnecessary hack that's easy to fix;  I'll do that.  But it would still be good to understand exactly where this is coming from.