WPF ComboBox not responding to mouse

Question

I have a very weird problem with a WPF ComboBox. On one computer (and only one) in our company the WPF ComboBox refuses to respond to mouse events when the ComboBox drop down is

Answer 1

I had a similar problem on Windows 7. Another idea is to play around with the display settings. My solution was to set the program to run with 256 colors using the compatibility settings of its shortcut.