Why is ChangeValue reentrant on a gtk_dialog_run?

["Boggess Rod" <rboggess corefurnace com>]

At the risk of beating a dead horse, I've figured out what the problem
is, I just don't understand why it's occurring or how to fix it.

If I call hscale's value-changed signal callback, I can return TRUE or
FALSE, and it behaves as expected.  If I create a static variable,
increment it, do a modulo 2 and return TRUE or FALSE on alternating
returns, in every case, it behaves as expected.

However, when I create a message dialog, it re-enters the value-changed
callback.  What's especially odd is that it re-enters when the message
dialog is created, not when it's actually gtk_dialog_run().

Is this a threading issue?  I thought I was running the message dialog
modally, and if so, they should be on the same thread.  Anyone know
where I can find more info on this?