I've written a modal pop-up [url removed, login to view] user control using JQuery, along with the JModal plugin.
It's very simple to call, inside of an [url removed, login to view] AJAX panel. It has two simple methods, Show() and Hide()
The only problem is that it only works perfectly in IE7. In FireFox, it appears yet the cursor disappears inside of the text boxes. In IE6, nothing happens at all.