I open .mov files in Photoshop in order to turn them into gifs. It will work 2-3 times fine, then the next time I get an error message saying "Could not complete your request because the video file could not be opened." I have to then quite and restart my entire computer for it to work again.
What Platform do you use. Apple does not support QuickTimeand from what I read QuickTime should not be installed on windows it is old code that has security issues on windows. If you are on a Mac it may be an Apple issue Photoshop would be using Apple QuickTime support. QuickTime is not on my Windows system ant is not an export video option in Photoshop. QuickTime videos do not play on my system for the QuickTime codecs are not installed. A quickTime video would can not be opened on my system if its encoded with an Apple QuickTime Codec.
I'm on a mac. I render a video as a .mov in After Effects then open it in Photoshop in order to make it into a gif. It will work for a while then suddenly just stop working.