Try to save the attachment to disk and open it with the desired program.

This affects me with Thunderbird with large jpg files. (TB 24.5.0)

The same files which crash Thunderbird will also crash Firefox if you try to open them with it. (FF29)

They will open fine in any image program I possess, or any other web browser, so I'm assuming it is a Gecko problem?

The crash of either T-Bird or FF is also kicking me out of my session, so I have to login again.

Open the files in an image viewer, convert them to any other file type (e.g. tif) they open fine in T-bird and FF.

No - this is still an issue only with photo's. When I try to open my photo's the Microsoft Live Gallery quickly flashes and then disappears. These are the same photo's i was able to open 2 weeks ago. i looked in the settings and I can't find anything that looks incorrect.

lets just slow this down.

When you open a mail the jpegs are attached to, they should appear in the email at the end. Do they do that?

No, Thunderbird crashes before the photos load. If I save the message as a .eml file, I can then decode the images from the base64 code in the source, and save them that way, but it's a very long way round to look at a picture. Firefox doesn't do anything except crash when you use Ctrl+O to open one of the saved images

Not talking to your bwucie, if you have an issue and it appears you do please post a new support topic as your issue and theoriginal posters are only related in the use of JPG and having two questions on the same thread is confusing to everyone.

When creating your support topic, please include the size of the JPEGs and if possible the sending mail client, the generating program and anything else that might be relevant to figuring out what is happening.