You forgot to mention what version of iMovie you have, so:
iMovie 11 - cameras supported:
iMovie 9 - cameras supported:
iMovie 8 Camcorders supported:
Digital camera RAW formats supported by OS X Lion:
Digital camera RAW formats supported by OS X Snow Leopard:
What format are the video files in?
Not as such, more to do with the incompatability of .mod files and iMovie!
This is an older reply to a different problem (JVC's TOD files and Quicktime) but may contain a pointer:
JVC released the Quicktime Components update:
which should take care of TOD files playing in Quicktime, but:
The answer to your question depends on which model JVC camcorder you have.
Here are a few basics:
1. If you have a JVC HD Everio that records in the AVCHD high definition file format (.mts file extension), and you have an Mac with an Intel processor, (sound like you do) running iMovie '08 or '09, then it should be no problem. Simply connect the camcorder via USB and launch iMovie.
2. If you have a slightly older JVC HD Everio that records MPEG2 high definition (.tod file format), then it is easiest if you record in the special 1440CBR mode, and transfer your video to your Mac using an i.Link (Firewire Connection) using the "Playlist Dubbing" process which is explained in your owner's manual.
See also this post from Chris at JVC dated March 4, 2010 at the end of this thread:
If you have further problems contact JVC.