I have had my fun today with this issue, so let me add what I can to the discussion.
About a month back, I was preparing a number of iPads for a staff training. I had 20 camera connection kits, and 20 SD cards, and the instructor wanted me to pre-load some images on the cards. So, to make sure it worked, I pre-loaded the pics and then tried to use the connection kit to get the pics on the pads. Wouldn't work. Tried all kinds of formats. Began to think of new cuss words. Long story short, the SD card has to have a folder labeled DCIM, just like some of the above comments have talked about. You create the folder, put your pics in it, and Bob's your uncle! Everything works fine. That is, until today.
We we're trying to load some pics onto about 9 pads that have the new iOS, and we couldn't get the camera connection kits to work. However, we had 1 pad with the old iOS, and it worked fine. So, used the camera connection kit to link the iPad with old iOS to the ones with the new iOS (one at a time of course) and we were able to transfer the pics that way.
Why the pics wouldn't load on the iPads with the new iOS is still a mystery. However, given the above comments, and this experience, I think we can safely conclude that the problem has to do with the new iOS.