Sorry i just tested it and it occurs with the open/save file as well. This might be that Firefox 27 doesn’t seem to have access to the file system, may be blocked by Avast.
More more links attached from other user’s.
https://support.mozilla.org/fr/questions/986530
https://support.mozilla.org/en-US/questions/986151
http://forums.mozillazine.org/viewtopic.php?f=38&t=2801993
PS: I don’t have PhotoMe add-on installed and i really don’t want to switch to another AV, thanks.