I had similar problems with my Sony a while ago. I avoided iPhoto and dragged all the images from the camera to a new folder on the desktop.
Then you can either try to import them to iPhoto from there or, if that still fails, open them in Preview and do a "Save As..." in any form you like, maybe even .jpg again and see if iPhoto recognises them then.
Pretty tedious, but if it works...
My problem was solved by a software upgrade from Sony.
Are you aware that there is a "hidden" application called Image Capture that is the thing that actually recognies that a camera is connected and tells iPhoto to open? You can check Image Capture preferences. Image Capture is in the Applications folder. The problem I had was traced to Image Capture. The method I described above by-passes Image Capture.