I have never heard of this type of behavior.
It sounds like a card reader problem.
I would take your memory card to a photofinisher (like WalMart) and use one of their customer operated machines to look at the photos on the card and see if you can view the ones past 100.
If you can, the problem must be a limitation in your card reader.
I ahve a Panasonic FZ-20 and am using a Mach Speed 516 MB SD memory card.
When I use the camera to down load images everything works fine.
When I down load using my 6in1 card reader it works fine if I have under 100 images on the card.
At some level above 100 images (not allways the same number) it does not down load all the files.
If I try to view the files directly from the card I get a damaged file message.
If I use the camera I get the images.
Any idea what is wrong? How to Fix?