To reproduce this bug:

1. open the view org.mitk.gui.qt.ultrasound
2. new video device
3. choose "Video Source" = "From File" and take a video file (e.g. avi, mp4) that can be played on your system
4. add the device
5. activate the device => either instantly or after a few seconds an error "An error occurred: device or resource busy: device or resource busy" occurs

(if the option "greyscale image" is disabled some videos play for a short period of time and a crash occurs without an error message)