Amy,
It looks like you might have a content placeholder in the <head> of your master page. If so, you can usually remove it. That probably won't fix the main issue but at least your page editor will go back to normal.
After that's taken care of, we can tackle the content insertion thing. By the way, do you mind posting the jQuery code up? It could simply be an issue with the selector being used to target your...target. :)
-Tim