One of more field types are not installed properly

If you have ever come across the error One of more field types are not installed properly then you know it isn't easy to fix. If it happens in a query download the U2U CAML Builder as described in the blog.

Unfortunately I get the error when I try to delete the field from SharePoint using oDocLib.Fields.Delete(). Any ideas why this happens would be appreciated.

Fortunately this blog gave me some hints.