I had a problem getting the AdventureWorks sample database that I installed to run under Vista RC1. SQL Server Management Studio kept reporting an error when I tried to access either the AdventureWorks or AdventureWorksDW databases. To get around this, I discovered that I needed to add my Windows user account to the sysadmin server role. After doing this, I was able to access both databases.
On a side note, I can't get SQL Server 2005 SP1 to install. It keeps prompting with a dialog box reading "Error performing inpage operation" regardless of whether or not I run the installer as administrator. Looks like I'm stuck waiting for SQL Server 2005 SP2 for this to work right.