If you have latest TVersity installed on your PC with the correct filters and codecs for transcoding it should transcode the diggnation podcast to divx for playback on the N800. If it does not, which sounds to be the case, I would ask some specific questions in the TVersity forum as Ronen and others are very helpful.

It would be really great if more Nokia Internet Tablet users provided feedback to show interest in TVersities developments http://forums.tversity.com/viewforum.php?f=2

Bit busy at the moment but will try diggnation video podcast, what's the URL you are using etc.

Edit, did you try the wmv feed? http://revision3.com/diggnation/feed/wmv-large