So you're saying that you get the same results when you save the jpg-file to
your hard disk first and then try to open it? In that case it is not an
Outlook issue but an issue with that jpg-file instead. Ask the original
sender if he/she can resend it to you.
A possible Outlook related issue that may have caused it is that your virus
scanner corrupted it while the message was received. If your virus scanner
integrates with Outlook, disable this integration, ask for the picture to be
resend to you and try opening it again.
See
http://msoutlook.info/question/20