Have you downloaded the updated codecs from Apple: Apple Menu/Download Additional Content?
Here is the direct link: http://support.apple.com/downloads/
I have a Sony Nex VG-20 which is AVCHD, I am able to import, create optimized, etc. No issue.
Is the original directory structure on your cards un altered? i.e., have you renamed clips ON the card while in Finder?
So this is the folder created by FCP 10.1.1 - inside of fcpbundle.Library at the root of your external drive. Right?
(In the finder, one can rt. click on the Library Icons created by FCP 10.1.1, open show package contents/project folders) <-- that "secret" folder? Right? Not a folder that was left over from a previous incarnation of FCP X or one that you created in the Finder. Right?
Thanks in advance...
In the future, you might want to check ClipWrap.
I download from my SD card (via the iMac SD slot) all my AVCHD (Sony HXR-NX30U) clips into ClipWrap and convert them into ProRes 422. I keep them in a HOLD file for preview in QT and further delete and/or rough trim if necessairy.
Once I have made up my "editing" mind, I import the required media into my FCPX event. I never had any issue with the ProRes format..