The SQL update has been giving everyone a headache as of late. To better assist you we will need to information found in the hotfix log folder. These files can be found at: C:\Program Files\Microsoft SQL Server\90\Setup Bootstrap\Logs\Hotfix\

There should by three types of logs available, and each will be numbered by attempt to install the fix. Simply grab the highest numbered "Summary.txt", and post it's contents here. That will provide us with the error code for SQL Server.