Thanks for the tip. I'm not sure how to reset Photoshop CC 2014 preferences but I would like to give that a try before reinstalling.
Elsewhere, I have read that problems with RAW file compatibility arises when Photoshop CC 2014 resides on the same drive as Photoshop CC or other previous versions of Photoshop. As well as Photoshop CC 2014, I have Photoshop CC (I'm surprised that CC 2014 did not overwrite CC) and Photoshop CS 5, which I am reluctant to deinstall, in case I ever decided to stop my CC subscription. Can you confirm that this is the case?
I have halfway solved the RAW problem by downloading the Adobe DNG Converter. Camera .CR2 RAW files still do not open in Photoshop CC 2014 (nor did they previously in Photoshop CC) though I believe they should but once converted to .dng there's no problem.