More details. These problems are new with equipment I have used before successfully. My CF cards are either 8 or 16gb, inserted into a Calumet Photo external card reader. The CF cards have been used in Nikon D700 or D800 bodies. One card had images from both cameras, but usually they are all from one. In the import interface the mounted card wouldn't eject, and when it was selected it showed the file structure of the main hard drive of the computer not the CF Card. No it has started doing something it hadn't in a while, showing the same CF disk icon twice in the list. One shows the images, the other appears empty.
I inserted an SD card from a point and shoot camera and it was behaving. Initially I couldn't import from the hard drive either, but that has now started to work.
I recently updated my system to 10.7.5, and was then prompted to update Aperture to 3.4.5, but the problem had started before the update. Happened with two libraries. Restarting my system to see if that clears things up.