I thought I was the only one having that problem. It all seemed to start when I updated Quicktime player from 6.whatever to 7.0.3. iTunes stopped working, and Quicktime too. Just like you described, I click on the icon in the dock, and after it bounces up and down for a moment, it get's the black triangle under it like it's an open app, but no window opens, and no iTunes or Quicktime.
What the freak is up with this?!