Category Feed Issue

I have a problem with category feeds not working.

At the moment the feed for the site works fine
http://www.buttonmasher.co.nz/feed

But category feeds do not.
This would not normally be a problem but as we have a podcast I need a functioning feed for it to work in iTunes.

http://www.buttonmasher.co.nz/category/podcast/feed

The problem is not limited to the pocast category, it seems that non of them work, but the podcast category is my main concern.

Any help you could offer would be fantastic