Some camcorders have a new Pre-Record function which, when enabled, continuously records several seconds of images into an internal buffer memory which helps capture sudden shooting opportunities. Enabling that mode, however, may cause not being able to preview video while importing in iMovie '08.
Camcorders known to have this option include:
Panasonic HDC-SX5 AVCHD DVD
Panasonic HDC-SD5 AVCHD...