QButtonGroup setExclusive Mac problem

I've written some code using a QButtonGroup where I've got a bunch of buttons where only one of them can be on at a time. Therefore I've set the setExclusive flag to true. This works fine with the code running in Linux, but not on the Mac (OSX 10.6) where the buttons usually stay highlighted. It seems this flag doesn't work on the Mac version. To me this looks like a bug in the Mac code, is this known, and is there a simple workaround?

Another problem with the Mac version of QButtonGroup is that with my bunch of 7 buttons (they are all simple QPushButtons) the last one gets given a different appearance. The first 6 have the oval appearance (as in a running track oval, not an ellipse), but the last one is just big rectangle. Again under Linux they look fine.

Is this Mac version just a bit buggy?

AFAIK I'm running Qt4.6 at least on each OS.