Incompatibility with Vista Inspirat Pack on windows XP

When using on windows XP a visual style for the windows and buttons (in my case the Vista Inspirat Pack) you get a bug affecting the display of QT widgets in QT Designer (not Creator) and some applications using QT (see files attached). You only see the bottom part of the widget, but surprisingly when you right clik in the grey area where the rest of the widget should be you do access the contextual menu of that widget (where as you don't get anything if you click below the widget for instance). When I found out where the bug was coming from, I installed Vista Inspirat Pack on the other computer to make a test and got the same problem, so it's definitively an incompatibilty with QT, but I don't know more, my solution for now is to reapply the default windows XP appearance...