Photoshop CC can open old files but suddenly cant create new ones

I've been using Photoshop fine for ages and this is the first time I've ever had a problem.

I suddenly can't create any new files in PS CC. One second it was running smoothly and the next I cant do anything. After picking the size and clicking Create, nothing happens. I can, however, still drag images into Photoshop and it opens them. But it won't save any adjustments to them. It shows a quick saving progress bar but the images are not actually saved.

Some of the tools are also playing up. For example, the Elliptical Marquee Tool doesn't follow my mouse. It selects random areas of my image. I also can't merge or flatten layers suddenly. The options are available, and are clickable but when I click them nothing happens.

When I use the Brush tool, after releasing my mouse the lines vanish. Sometimes they stay. It's all very random.

I have no idea what is going on.