Hi
Have the exact same problem in iMovie HD.
The files on the camcorder hard drive are MPGs. Once you have located them drag them to a folder on your mac and then convert them to another format using some 3rd party freeware. I used iSquint and converted them to mp4 using the TV quality function.
I found that turning the camera on and off had no effect and the drive wouldnt show up on my desktop even when the camcorder was plugged into its dock. Hitting the disk burn button on the dock them made the drive appear on the desk top. Don't know if you have that issue as well.
Whilst by no means the best way it suited what I was doing at the time so it may serve as a temp fix for you. Getting your hands on better quality file conversion software is the way forward as SONY are very much limiting themselves.
I should mention that this camcorder was tried on several windows machines as well and the files wouldn't load to the 3rd party editing suite so at least the mac has a fairly quick solution to this.
At the end of the day the fault is with SONY so perhaps a different make of camcorder when you come to get a new one.
Admiral