No idea, why this version hasn´t been as rigorously tested as earlier versions. There are numerous changes to the main tables that come without any warning – numerous incompatibilities even with disabled plugins and the first time that I am really in trouble with WordPress. Fortunately I was working with backups and did a pre-flight. This is what I recommend
- go back to your last WORKING version of database and scripts
- DISABLE all plugins
- select the STANDARD THEME
- maybe you need to fake the database ID in the options table?
- delete all scripts except those in /WP-CONTENT
- copy the new scripts to the server
- login in as admin and wait until the system updated your database tables
- update also all PLUGINS and activate one by one EXCEPT UltimateTagWarrior
- import tags from UltimateTagWarrior under Admin/Manage/Import
- the current EventCalendar will disable your site search – leave it inactive for now
- select YOUR theme
The only thing that really helps is to cut and paste any error message into a google search: You may also want to check these links 1 + 2.
Sorry, if you see here occasionally popping up error messages – I am not sure if I really found all quirks.