I am only responding to share a similar experience as most of you and keep this post "fresh" for people who have recently had this problem.
1) look at all modules when deleting: i had added some but never used them, so i forgot they were there!
2) look under blocks AND activities: i deleted the blocks and used FTP to delete the folders from site and only recently found them under activities -- duh
3) i still also had to use phpmyadmin to clean up the "ghosts" tables as one poster called them. maybe if i would have deleted these before the upgrade i wouldn't have had to do this?
so far i think i've got it running again * sigh*
running 1.8.3 on Linux server