I'm assuming importing from the same camera and cf card has been successful for you in the past. Can you share a little more information? What type of camera? You menion an update ... an update of Aperture? Digital Raw? Both? Does the import work for some of the photos, but not all, or just bail entirely?
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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.
If the restart fails to be the magic wand, I'm wondering about a corrupted CF. I had a problem once where import would fail. Via trial and error, importing smaller batches of photos, I found several of the images were corrupted. Once import hit the bad images, it failed. This was an older version of Aperture 3.x.
Copying to the hard drive may succeed if the corruption is in areas digital camera raw cares about. Whereas a general copy (byte by byte) will work fine. The copy duplicates the bad data.
But if this is happening on all of your CF cards ... something else is afoot. I suppose you could try a quick experiment using iPhoto. If iPhoto works, it's certainly point the finger at Aperture.
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