Our teamcity build agent has been running on not user interactive mode. However some of our unit tests need to test that error messages were actually popping up. So the MessageBoxOption.ServiceNotification was added to the Messagebox.Show call. We created a method called KillMessagebox which uses Win32 Api to detect the Messagebox and kill the Messagebox. Everything worked fine until recently upgrade to version 9.1.5. Now the messagebox is either not popping up or silent goes away. Our KillMessagebox can't detect the messagebox any more. I have been trying to figure this problem out for a week now. If somebody can give me some help, I would really appreciate.