Qfontcombobox buggy?

[Jupiter]

i use a qfontcombobox in my app. when i open the menu to choose a font, i encounter 2 problems:
1st i takes pretty long until the menu is shown
2nd there are some empty entries, when i choose one of them my written text disappers until i choose another font

I'm using Qt 4.8.0 on Mac

[Jupiter]

also tested it on windows now, no problems there. 1 font f.e is STIXGeneral. can i filter them out somehow?