Another potential fix, which may prove to be much easier to manage in the long run, would be to upload your videos to YouTube or Vimeo and then embed the video code into an HTML page on your iWeb site.

The added benefit of doing this is those services will do the file conversion for you so you don't have to worry about encoding for the web, files sizes, or using extra bandwidth at your hosting company, since it's all taken care of for you.

Hope that helps.