Cubase 5, as opposed to earlier versions, supports only the QuickTime format; that is why the dropdown menu for "Playback Method" isn't available anymore. Our video problem (white thumbnails, no video) was solved by deleting the Cubase preferences, as suggested by a user on reddit (I posted my question there, as well). We did this by first removing all files in C:\Users\[username]\AppData\Roaming\Steinberg\Cubase 5 Then starting Cubase so it can regenerate those files, close it and then we could put back in some of our files like custom key commands, track presets etc.. Apparently something had barfed so letting Cubase regenerating all preferences was the solution.