PROBLEM
When you tried to install the service pack 1 for WSUS the setup failed.
If you open the log file "[UserTemp]\WSUSSetup.log" you see this error message.
Error MWUSSetup ExecuteQuery: Failed to execute SQL query BACKUP DATABASE SUSDB to DISK=N'[DRIVE]\[WSUS_FOLDER]\SUSDB.bak' (Error 0x80040E14)
Error MWUSSetup ExecuteQueryGetNoResults: Failed to execute query BACKUP DATABASE SUSDB to DISK=N'%s' (Error 0x80040E14)
Error MWUSSetup BackupDatabase: Failed to backup database (Error 0x80040E14)
Error MWUSSetup CUpgradeDriver::PerformSetup: Failed to backup database (Error 0x80040E14)
Error MWUSSetup CSetupDriver::LaunchSetup: Setup failed (Error 0x80040E14)
Error MWUSSetup DoInstall: Wsus setup failed (Error 0x80040E14)
CAUSE
The folder '[DRIVE]\[WSUS_FOLDER]\SUSDB.bak' does not exist and/or the permissions are not correct on it.
SOLUTION
1. Create the folder.
2. Set the "Full Control" permission to the "NETWORK SERVICE" account.