WSUS Install Problem on Windows Server 2008 SBS

Hi there. We are having problems installing the WSUS component of SBS 2008. When installing WSUS SP1 from Disc 2 of the original CDs, the setup process fails. I believe the problem is with the database. The following is taken from the setup log file:

StartServer starting...
Generating encryption key to write to the registry...
Generating encryption key to write to the database...
Generation of encryption key to save to the database failed. Error=System.IndexOutOfRangeException: Index was outside the bounds of the array.
   at Microsoft.UpdateServices.Internal.DatabaseAccess.GenericReadableRow.GetBoolean(Int32 index)
   at Microsoft.UpdateServices.Internal.ConfigurationTableRow.ReadRow(IDataRecord record)
   at Microsoft.UpdateServices.Internal.DatabaseAccess.AdminDataAccess.ExecuteSPGetConfiguration()
   at Microsoft.UpdateServices.Internal.BaseApi.UpdateServerConfiguration.Load()
   at Microsoft.UpdateServices.Setup.StartServer.StartServer.GenerateNewDatabaseEncryptionKey()
StartServer encountered errors. Exception=Index was outside the bounds of the array.