Qt font looks weird on OS X

Question

I just started using Qt (using Qt 5 beta 1), and found that the fonts displayed in OS X 10.6.8 are corrupted. I tried using different fonts, but they all look like the image I posted below (very thin, uneven). How can I display fonts correctly?

The code I use is simple:

#include <QApplication> #include <QLabel> int main(int argc, char *argv[]) { QApplication a(argc, argv); QLabel label("The quick brown fox jumps over the lazy dog..."); label.show(); return a.exec(); }