I have the same type of problem. The only way Photoshop CS6 will open a file is to completely shut down. When it opens up again it will only open one file,and then it goes back to the same problem. It also will not create a new canvas. When Iwas able to open the one file I tried using the brush tool.and it would just partially work. Just for the hell of it i switched my mouse and believe it or not everything went back to normal. The old mouse would work great in everything else such as Premiere etc. but not in photoshop. It was not a bettery problem in the mouse as they were new batteries, just something wrong with the mouse. I sincerely hope this works for everyone who is having this problem, as it was sooooo frustating. Let me know.