Apple has released an update to iMovie, bringing the version to 8.0.5 and adding improved compatibility with video capture devices. The update is 35.56MB and should be available through Software Update for people with iLife installed. It can also be downloaded here.
Specifically, the update includes the following:
Improved compatibility with camcorders using the iFrame video format
Improved compatibility with importing video captured on the iPod nano
Fixed problems with resizing the iMovie window during playback
The update is recommended for all iMovie '09 users, and requires OS X version 10.5.6 or later. If you are running a camcorder that uses the iFrame format, this update might be particularly useful for you, though in order to have an iFrame-capable camera you would have to go out and buy one of the first two released by Sanyo today.
CNET editor Jim Dalrymple has an article on the new iFrame format, with links to the cameras that support the new format. Check out Jim's article here: http://news.cnet.com/8301-13579_3-10374263-37.html