Yes, these files do not work in compressor (mp4 files from AVCHD).
You need setup a compressor setting in FCPX, and transcode that way, or import the AVCHD file in to FCPX which will rewrap the files to .mov, which you can then transcode in Compressor, or you can check out something like EditReady.
Adobe Media Encoder will also read them.
Jeremy