Huge thanks to Jonty. I logged out of Dropbox and got my Gallery back. Too scared to sign back in yet though, will wait for the problem to be fixed.:p I'm thinking it was the recent update from either Dropbox or Cloud, or maybe both.
I had exactly the same problem with a Samsung tab3 P5210, did as described above, turned Talk Back on even tho it said it was off then off and the annoying lady disappeared.