maybe it's not the phone that blows. have you tried to access the file from a computer to make sure it really is a jpeg.
also, if you haven't already, you may want to send yourself a jpeg to make sure you know what the file is... and make sure that the file is not too big to be opened.. I thought I heard there was a size limit.
There are a number of reasons why this can happen. First, there are a lot of different ways to save a JPEG and not all are as universally understood as we would hope. A lot of devices will not open a JPEG that is saved in any color environment other than RGB -- and a lot of people save them in lab color, indexed color or grayscale. Some JPEGs are also not saved in a format that is easily used by portable devices. Working in Photoshop, the best option is to use the "Save for Web and Devices" option -- this creates a very compatible file that works just about anywhere. The email application used to send the file can also affect the ability to open the attachment. Many times, the image is seen as embedded instead of attached.
I unloaded and reloaded the attachment service and it still does not open jpegs....I wiped messages and attachment items. I am taking phone back to Verizon for more help. I can open other attachments, just not jpegs... crazy.
Connected device to computer.
Started DM.
Uninstall attachment services.
Closed DM. (device was still connected to computer)
Restarted DM.
Installed attachment services.
Keep in mind, some of the attachments that weren't opening before, still weren't opening. However, I was able to view jpegs, pdf files, etc in all new emails.
Also, if you don't have any third party app installed for pdf files, you might only be able to view it in an email. I have never saved the file and tried to open it outside of my inbox. I usually click view attachment while i'm in the email. When I do it that way, I have been able to view the pdf file (regardless of the size).
This is not a guaranteed fix but it worked for me every time I had this issue. I have upgraded/downgraded my OS numerous times and this solution always worked whenever I had a problem viewing attachments.
As far as the jpeg you're trying to view...try sending it to yourself again. Maybe the file got corrupted somehow.