Photoshop CC 2017 - Error - "Can't write new document presets file." on close, files won't open

Hi all,

I've just updated to Photoshop CC 2017 and it's now not saving preferences, and won't open documents.

On closing, I get the dialog error "Can't write new document presets file."

I've tried resetting preferences, which hasn't worked. Is there a solution to this please?

Thanks,

David