Sounds you are having the same problem as me.
My problem stems from trying to capture NTSC video from a PAL device (although I suppose the opposite may also not work).
The video is playable from the camera and on an NTSC or PAL TV however when trying to import using iMovie it stops after a second and won't move on.
Have tried everything to try and sort this out and so far no luck.
I am resorting to borrowing a friends NTSC camera to try and get the video in this week.
Might be the same problem for you...