Problem with dialog overlay

Problem with dialog overlay

Hello

I'm using jquery 1.4.2 and jquery ui 1.8.4 versions. I have a webpage that opens a modal dialog which creates another modal dialog. When the first one opens the second dialog first time, there's no problem, but If I open the dialog a second chance the overlay of both dialogs disappear when I close it.

Do you know a solution to this problem???

Thanks in advance.