Podcasting problems

Hi, I’ve tried this a few times now and am still getting the same problem:
Basically WP1.5.2 doesn’t seem to be picking up my mp3 files linked into a post and producing a suitable podcast feed.

I’ve tried a few things which are the WP iPodCatter plugin, which does a good job of adding iTunes tags etc. I’ve also learned I can add a custom key to my post which gets me the mp3 file in the enclosure tag, but it is still missing the ‘length’ and ‘type’ data. If I could find out how to add those myself I would be happy, or better still, what is going wrong in the first place?

Thanks to everyone who can help.