QFileDialog hangs and can't select any files

For Qt4.8.5 and Mac 10.9GM

My code:
QString t_strFilePath = QFileDialog::getOpenFileName(this,
"Open",the dir parameter,"Image Files (*.png)");

1. Enable application sandbox

• Bug: The QFileDialog hangs sometimes.
• Bug: All files of the filedialog view is disable,
  you can't select any files(include *.png).

2. Disable application sandbox

• Everything is ok