We've had several users reporting this kind of issue with Firefox (not sure which version). We're trying to narrow down the problem, so please, all additional information is of value.
The thing I'd like you to try is to open your article, click the "Edit this article" button and...
- Try to upload additional photos and save,
...or if this does not work...
- Try to upload one additional photo and save.
Also, have you noted any error message(s)?
Thanks very much for trying,
/Martin