Dual List dialog box has no visible objects

Hi Everyone,
I'm having this problem with showing a Dual list box, this is a run time
problem, when I try to display a dual list box to the user, it comes up as
blank dialog box with no objects on it. this problem is interminant, so
sometimes it does behave normally, and sometimes it freeks out. I tried to
debug it, it seems it behaves normally in debug mode.

Any help is appreciated

Regards
Omar