Annoying behavior of QDialog after update to Qt 5.2.0

[rkhaotix]

Hello guys, how are you!?

I'm having a big headache with my project after update my Qt installation from 5.1.1 to 5.2.0.

All instances of classes that inherits QDialog on my project are having some delay when the user call them from the second time and so on... My first thought is that this behavior is being produced by the window manager (in my case KDE 4.8.5). I don't know how Qt and KDE communicates internally but when I disable all desktop effects (including composition) the dialogs works fine but when the desktop effects are on the dialogs opens with a delay of 2 seconds (approximately). Another detail is on Windows, MacOS and Linux (when using other WMs like Unity) all work fine!

I have attached a video in order to try to show this strange (and annoying!) behavior.

Sample video:
http://www.youtube.com/watch?v=1w82Fkak21U

Someone is facing this problem? What I'm doing wrong?

Thanks for any help.
P.S.: Sorry about my poor English. :)