I had experienced the problem with Opera, Safari, and Firefox (for Mac).
There was something wrong with the .jpg file. I was going to try and upload it from Windows before I responded, but the browsers above and IE refused to download the image (which I had put on my website to transfer from Mac OS). Also, Photoshop refused to reopen it, so I saved a new file from the .psd and everything worked...
Sorry for this waste of a thread.