Smugmug even has a similar issue, as you typically look at the photos without the jpg file name (I played with this recently on another travel site). For instance, this is a page where I have some Lake Tahoe photos, but as you're not highlighting one specific photo in jpg format it won't display (though the link is fine for anyone clicking through). It won't display as an image file, so here's the plain link.
http://tom911.smugmug.com/gallery/33...186566812-L-LB

However, if I click on the same photo, and ask to "view image", it will display it as a jpg, and then if I use that link, it will display.