Applications :: Compatible Video Format For IMovie

I have a bunch of videos that I recorded on my windows computer, they're in an uncompressed AVI format (huge files). Since I wanted to use iMovie 09 for the editing I decided to convert them to mp4 using VisualHub (to compress them and so they would work with iMovie) and they seemed to work fine, I could still see the video on Quicktime. The problem is that I still can't add them to iMovie. Whenever I add one of these videos as mp4 or dv (I've tried both) they go through the process of adding them to iMovie (copying, creating thumbnails, etc.) and then when it's finished, that's it. No video is actually added to the event. It happens all the time no matter what other options I change when converting the file. And by the way, I noticed the "Show All Clips" option at the bottom of the iMovie main window, it's not that. Anyway, here's the info on one of the files (from the Quicktime X info page of the video):

File: Video 4.mp4
Format: H.264, 800 x 600, Millions, AAC, 2 channels, 44100 Hz
FPS: 30
Data Size: 84.3 MB
Data Rate: 4,505.10 kbit/s
(This file goes through the process when I add it to iMovie, but doesn't actually get added). Some of them have an 840 x 524 size instead of 800 x 600, but they still fail to get added to iMovie properly.