dialog#run seems to block other threads

I'm writing a multithreaded lablgtk2 program and to cut to the chase
it appears that the dialog#run method prevents another OCaml thread
from running.  It is as if the GC lock isn't being relinquished.

Threading works fine for the main window and I thinking I'm linking
the program correctly and using GtkThread.main as required.

While this may still turn out to be a bug in my program, I'm wondering
if this is supposed to work, or could this be a known bug in lablgtk2?

Version: ocaml-lablgtk-2.14.0-4.fc13.i686

Rich.

-- 
Richard Jones
Red Hat