There are no propper settings, only a variety of choices. It all depends on what format you want top shoot: 720p24 or 1080p24. Without that information not even a JVC guy can tell you how settings should be in FCP.
I saw this same message last week when we demo'ed a 700. In our case, the camera was set to shoot in 1080P and we were trying to review a clip on the SDHC card that was shot at 720. all we had to do was put the camera in the same record mode as the clip, and VIOLA, we could review the footage.
Now, if you're getting this message in FCP, it sounds to me like you're having a similar issue.