I am still using wordpress mu 2.9.2. I have setup 2 test domains before i upgraded to 3.0. the test domains are mirrors of my production domain with 8 sites and around 9-10 plugins.
i varied the upgrade process for the test domains from using the automatic upgrade on the first one to doing the manual upgrade on the second. As well, i disabled all plugins and switched the theme to the default theme for both test sites.
Using the automatic upgrade it says that wordpress has been updated... but it does not give me the button/link to go back to the dashboard. trying to get to wp-admin results in a timeout or eventually a 500 error. the front end still works however.
Using the manual upgrade it will just not let me get to the wp-admin. the front end also works after this upgrade.
this is really baffling as to why it will not update. i have a whole production site ready to be updated and use the new features of the 3.0+ update.
any help is greatly appreciated.