I have never had a problem with a WordPress upgrade, and I have been upgrading it for years. 3.3 looks great, but it has done something very odd to one of my WordPress Networks.
I have several problems, probably all related.
1. I can't access the back end of ANY of my child sites in this network. They are all domain mapped using a plugin, but I get a "Error 500" message if I try to access the admin panel of any of them. Or, I get a "Nothing found" error on the front end of the website when trying to access one of the child domains at http://childomain.com/wp-admin. I am sure that this problem has something to do with #2.
#2. I can't update my network to 3.3. I upgraded the main site, sort of (it isn't working like it should be), but the automatic upgrade process is not working for the remaining sites.
#3. The main site dies. This is hard to explain, but I will do my best. During the original upgrade process of the main site, the upgrade froze and did not complete. This ruined my network temporarily, and it took me 2 manual upgrades and a database repair to fix it. Now I can access the main site (domain mapped) and the admin panel of the main site, but only sometimes. Other times, I get a "Page not found" error, regardless of the browser I use. It's like my browser can't find the domain. I have also gotten a "Error 500" when accessing the admin panel. When I try to upgrade child sites, this happens, and when I try to access the front end of child sites this happens.
#4. I can't make or save any changes to any of the plugins on the Network Admin screen.
I need to figure this out ASAP. This is affecting several other completely separate installations (like vBulletin), I assume because of the domain mapping. Why or what would cause this? Starting over again isn't an option because of the nature of the websites. Downgrading to 3.2.1 isn't really an option, either, as I can't downgrade the database. (Dumb, I know.) I appreciate any light anyone may be able to shed on this as I am completely at a loss. Thanks in advance!