Just a quick tip/reminder.
I was looking through my error.log as part of testing and setting up a new site and found quite a few errors which start similar to this:
" WordPress database error Table '4_posts' doesn't exist for query SELECT post_name FROM wpwp_4_posts WHERE post_name = 'feeds-for-google-alerts' AND post_type = 'post' AND ID != 0 LIMIT 1 made by do_action_ref_array, call_user_func_array, ab_process_autoblog_for_cron, autoblogcron->alway..."
Anyway... The upshot of this is:
These errors will occur when you delete a site which has autoblog feeds set up but aren't removed before you delete the site. It also looks as if AutoBlog will attempt to post these in the main site once the sub-domain site is deleted.
It might be a good idea to remember to check AutoBlog before deleting any sites to see if there's any feeds set up.