Category permalinks

Hi, I’m having a problem with my categories and permalinks. Well perhaps not a problem perhaps I just don’t understand how to do this.

I have a couple of categories.
General News
Green News

My permalink structure is setup so that my posts look like
url/blog/year/month/day/post-slug.htm

Say the post is under category green-news, I would like all that news to show up under
url/blog/green-news

Here is an actual link to my site.
http://www.canadiandriver.com/thenews/2008/04/22/plug-in-hybrid-study-to-be-launched-in-quebec.htm

The above link goes to a post that is part of both “general-news” and “green-news” but when going to:
http://www.canadiandriver.com/thenews/general-news I get a 404 page.

What am I missing here? Thanks for any help!