[Discuss] Peculiar JPEG Image behaviour -- Off Topic?

[Murray Strome]

i received three JPEG images in full resolution sent by someone with a 
Mac computer. They were all "full resolution", and a bit over 2 MB is 
size.  I tried to open them with the GIMP (2.2).  In one case, it took 
about 30 minutes to open. On the lower bar, it said the background was 
about 900MB.  During the opening of the image, the computer pretty well 
ground to a halt. I did some editing and tried to save it again, but 
after an hour of churning away, using 85% of the computer's 1GB RAM, it 
still wasn't saved and I was really unable to do anything else with the 
computer because the response was so slow, so I killed the application.  
I was able to open it using Gwenview, then save it, then open it with 
the GIMP. It was still pretty big, so I created a new file, copied and 
pasted the image I had opened with the GIMP into it, then  saved it.  
That image opened OK. 

One of the images gave this error when trying to open it in the GIMP:

Opening '/tmp/P5010021.JPG' failed: Plug-In could not open image

I found I could upload the image to Google's Picasa2 with no problem. I 
downloaded the image from the website, tried to open it with the GIMP 
and had the same problem. I can preview it OK, and the EXIF data under 
properties all looks OK. There must be something about the JPEG format 
full resolution images are saved with the Mac to cause this (I think).

I found the same problem when I tried to open it with the GIMP in Windows.

Does anyone have any idea as to what is going on?  I have never seen 
anything like this before.

Murray