Hey,
If anyone has been using the AjaxControlToolkit and trying to nest
modalPopups, and has found that instead of a nested modalPopup opening,
its parent is closing (this is really annoying), I have one small part of a solution for you.
the first thing you should do is make sure any relevant UpdatePanels are set to
UpdateMode=Conditional.
UpdateMode=Always is the default and that's no good.
Seems simple, I know...
That's because it is. It's just one of those things that you have to think
of and if you happen to miss it could cause you a lot of confusion. I don't
know why Always is the default, because it seems like you'd almost never want
that behavior, but that's a mystery for the ages.
Unfortunately this didn't fix my problems in every case, but it was a start.