> Make sure to run your ruby code in only one thread at a time and only 
> from the "main" thread (?)

Well, I'm making sure to call it from a single thread, but I can't force
to do it from the main one. I'm writing an extension for a 3rd party
app, which calls my code from whatever thread it wants to, and it's
definitely not the main one.

> You could post backtraces, as well.

I'd be glad to, but as I've said already, I have no logs (at least not
at this level), and no terminal output from the app involved. All I get
is a dialog window from the MS Visual Runtime telling me about the
crash, without any usable details.

The weird part is that non-network code (even usong multiple ruby
threads) runs without problems.