Feedwordpress errors in wp 2.1

[oast]

I haven't tried, but I imagine you will need to change the database calls, specifically the category calls.
http://codex.wordpress.org/Database_..._wp_categories is the new format
http://codex.wordpress.org/Database_Description/2.0 is the old

There are a number of differences. That will get you up and running again

As far as generating new categories on your site.. you can set aliases in your existing categories so FWP inserts them into these if the spelling is slighly different. I look at feeds first to see what categories it is using, update my alias to conform then import the feed

Look at the 'Categories' section of the docs of FWP for more info. Same can be done if you utilise author links