This usually indicates spanned files that we treat as one logical clip. You can delete the extra copies, and in the future using the media browser to find your clips will bring them in as single copies.
Thanks, Steve. I'll do that next time.
It will help if you copy the whole camcorder drives files and folders intact onto your hard drive
The AVCHD protocol has a specific folder and file structure and information about the files is held in another folder
Also if you do have spanned files do not upgrade to CS6 as that has a major bug that Adobe has so far failed to fix