There is an article for about deleting the article types here:
Have you tried a rebuild of the knowledge base for the open link error?
Hi Calvin --
Thanks for the speedy response. Rebuilding the knowledge base fixed the open article issue. I noticed that it hasn't been rebuilt since two months ago although it's set to rebuild every weekday. I'll check into that.
I'm going to start creating the queries from the article you linked and see if that works to delete article types.