I've reported this problem 2 years ago: https://bugzilla.redhat.com/show_bug.cgi?id=541055
The problem is still present in F15 KDE Spin. ¿Could we please find some kind of solution? Again, I'm willing to help in any way, but I think that this problem must be priorized by the KDE SIG, especially since Anaconda devs have stated that they will not fix the problem (see comment 6).
Kevin Kofler suggested to create a kdialog wrapper. Is it possible? I think even I can help with that part of the solution.