The followng was suggested by another poster...Re: CANON 550D not displayed on iMac - how import movies in Final Cut Expre
The Canon EOS Utility should enable you to download both stills +and video+ from your 550D.
I don't think you will see the camera on the desktop or in the Finder (My Canon cameras never show up on the desktop or Finder when I connect & download, but Image Capture and iPhoto both communicate with the camera and download images & video. I never installed the Canon utility.)
The EOS Utility should see the camera and from there you should be able to download stills and video to your hard drive. +Is this working or not?+
The following discussion threads may be of some help to you, click on the links below to be directed to them...
Canon EOS utility updated to work in OS X Lion
click on the links...