Re: Photoshop CC 2014 (same happens in illustrator). Filter gallery (not greyed out, file is regular 8bit rgb) will not work. Error message "the operation could not be completed". Tried throwing out preferences etc.

Ok, it seems this is beyond what I can offer and I don't want to suggest anything that can make it worse. 

If you ever find out what it was, can you let us know?

We might be able to help someone else.

Gene