iPhoto cannot recognize JPG images -- what else to try?

I have a brand new MacBook Pro, and iPhoto refuses to import any jpg image. Here is a brief summary of the problems and attempts to fix it.

I used the migration assistant to copy over everything from my old laptop. When I opened iPhoto, all my events were there, but none of the images could be viewed (only thumbnails). When trying to import any new image (jpg), iPhoto says it cannot recognize file format. So the problem seems to be iPhoto not recognizing the files.

Attempted solutions:
- Rebuild library by holding cmd-opt when starting
- Check that images are indeed using RGB color model
- suspecting old account settings/preferences, I created a brand new clean account, and had the exact same problem
- took a picture with Photo Booth, pressed the button to transfer to iPhoto, does not recognize
- downloaded a random jpg, iPhoto will not recognize
- Reinstalled iPhoto from Apple DVD, repeated all of the above -- still refuses to recognize jpgs or any other image

I am now rather stumped. Any advice is appreciated. Apologies if this is answered elsewhere -- I could not find a solution.