This has happened a couple of times this evening, when I tried to first update an entry in Leicester with more images. I thought it was because the pictures were too big in size. I just gave up and thought I would try again another day.
The second time (the next time I used Dashboard), I tried to create a new entry, this time for Bristol. I got all the way to posting it, and i got the same error message. This time, I took a screenshot: