Ahha! Found it. When I upgraded, it seems I cleaned out the "NULL" in the categories.db a little too well, as I removed the "|"s that went with them. I tried adding a new category, went in and looked at the categories.db and saw that it added 6 "|" on the end, i.e. Ugly_Cars/Pacer| || || | so, I went in and found an unaltered copy of my old categories.db and removed ONLY the NULL's and now everything works fine, and it also solved the "Unkown Tag: Category" in the email sent to the submitter upon validation.
PS - there are no spaces between the "|" in my example above, but when I post this message, the spaces magically appear
[This message has been edited by Catriona (edited December 22, 1999).]
[This message has been edited by Catriona (edited December 22, 1999).]