Using qt-opensource-windows-x86-msvc2010_opengl-5.3.0-RC_2014-04-15_00-54-08-58.exe on Windows.

Run the gallery example in Base style. Try opening the combo box menu by clicking on the drop down button. Only the right half of the button is responsive to clicks. When you click on the left halp of the drop down button, the menu is not opened, instead it gives focus to the line edit.

Can reproduce on Linus Linux as well.