It looks like Firefox pushed out an update on July 4th.
We are looking into what might be causing trouble with the newest version.
In the meantime, reverting to the previous version of Firefox will solve the problem of saving photos with correct file names.
See this link:
https://support.mozilla.org/en-US/kb...ion-of-firefox
Reverting back to Firefox
38.0.5 should provide a temporary fix for member's experiencing this problem.
NOTE: You may need to first disable automatic updates to prevent being forced to use Firefox 39.