I have a massive MOSS content database that I'm trying to upgrade to 2010 via a database attach. After the process is complete, I get "Server error: http://go.microsoft.com/fwlink?LinkID=177673" when I browse to the site. Can't see anything obvious in the logs.
It seems that the error stems from the database being the wrong 'version'. I eventually fixed it by running upgrade-spcontentdatabase from powershell.