I was declaring the rating control in a code-behind page, as such:
Rating rating = new Rating();
cell.Controls.Add(rating);
Then below it, I was setting all the properties like you would any other control. Well, that didn't work because I kept getting an error, with the targeted control ID from the ExtenderControlBase class. I suspected that the problem was I didn't have a unique ID setup correctly, so I played around with that, and the correct solution I got to work without error was this:
Rating rating = new Rating();
rating.ID = "rating" + _extenderCount.ToString();
_extenderCount += 1;
cell.Controls.Add(rating);
_extenderCount is a local variable that gets killed at the end of the page lifecycle, just used to ensure the name is unique.
Everytime I go out to the web to find the RSS 2.0 specification, I always go to this site:
http://blogs.law.harvard.edu/tech/rss. This is because of how well it explains the format. I thought I post that in case it helps someone else.