Do you get a crash report or error message presented when this occurs? I might try swapping out the cable from one camera on the different machine to check that. Do you have another computer to test this camera setup? I am suggesting these steps to help isolate and identify what the issue might be. While rare, cameras can fail, as well as intermittent cable issues. What do you have set for ‘Camera Capture System’ in the ‘Settings’ window (click gears icon top-center)?