Firefox does sometimes not completely refresh after you’ve changed a setting on a page. To see if it is current go to the page, press the “shift” key and click on the “refresh” button. I’ve had to do this with several sites to see new content.
Also you could check out feedburner.com for possible answers as they helped me set up separate RSS feeds for several blogs.
I am having the very same issue. Kinda annoying though I am using a hosted wordpress but I put in the code you recommended Matt and it still seems to have done nothing.
