When activating an USVideoDevice no image appears and the mouse pointer shows that the Application is loading and loading and loading, but nothing happens. I debugged into it and it seems to be a deadlock caused by the update of ServiceProperties of the USVideoDevice.
I did not tested the behavior under Windows but last time i used the USVideoDevice under Windows everything worked fine and there were no changes to it since. Seems to be a special Linux issue.
As far as i know a similar bug once occurred in the IGT-Module. Also just under Linux. Windows seems to ignore this locking-problem.