Upgrading Wordpress

I've been updating a bunch of Wordpress blogs over the past few hours, and so far everything has gone pretty smoothly (I end up having to manually delete an option from a replicated database for each blog I update). The upgrades I'm doing include the Wordpress software itself, K2, and a change from using Spam Karma 2 to WP-Spamfree. Spam Karma worked very well, but it was pretty heavy duty, complicated, and not GPL. Since Wp-SpamFree is GPL, I've already started to work on it! :-) So far I have only changed the way it created a random key code - I like to use /dev/urandom, but Windows folks don't have that luxury. Now I'm running into an issue where I have to keep deleting a wordpress option in a replicated database:

delete from wp_options where option_name='category_children';

Doh! I tried to investigate why this is happening but didn't get very far.