Try checking:
Control Panel » Feature Settings-Attachments
Allowed Attachment File Extensions:
Separate with a comma.
.php,.php3,.php4,.cgi,.pl,.exe,.bat,.reg not accepted.
Make sure JPG is a allowed extension.
You have had this issue for a long time.
I was looking at your prior posts.
Maybe it is time for someone to look under the hood.
Last edited by Ruben; 08/12/2015 4:19 PM. Reason: Added Comment