I had lots of things it could have been..
- DNN 4.6
- Use of FriendlyURLs
- having a proper domain in front
So i got it back onto my local environment and started removing bits. Eventually I discovered it was the fact i was using geekgirlblogs.com instead of www.geekgirlblogs.com for portal alias of the site.
So as soon as if changed the alias to the www version tada..the rss was working again. Pity it took me so long to try that!