Wanted to share this with the group (though it may not be news for you all); this morning I ran into an issue I didn't even consider possible until now. We found that a particular .jpg image would render in FF, Chrome, etc, but NOT in IE.
As it turns out, the problem was due to the images being saved with a CMYK color space, and not RGB. IE of course doesn't know what to do with CMYK, so it shows a broken image. Changing the color space on the image to RGB did the trick.
The part that was news to me was that JPG even supported CMYK; as far as I knew, JPG only supported RGB, but I was (clearly) wrong.
Anyhow - hope this may help someone.