If the ads don't really bother you, or you are against ad blocking, feel free to ignore this post.
This works in XP, Vista, and Windows 7. Here's how you can watch the live stream on HD's main page and other ustream videos while bypassing the advertisements which periodically pop up from the bottom of the video. Taken from: http://www.tomnliz.com/Livecam/Ads.html
1. Go to start > RUN
2. Type notepad c:\windows\system32\drivers\etc\hosts
3. Add the lines:
127.0.0.1 imageads.googleadservices.com #[Tracking.Cookie]
4. Save the file and close it. If you have your browser currently open you will have to close it and reload it for it to start blocking those 2 entries above.
I tested this out tonight, working beautifully.