I have been installing a new dual-server installation of TFS this week and I have come across a problem when I try to install SQL SP1 on the data tier. I have started by following the TFS Installation Guide and after the initial SQL 2005 (Std Edn) install, I have chosen to install SQL 2005 SP1 rather than install just the hotfix.
A quick run of en_SQL_server_sp1_x86.exe kicks off the SQL Service Pack 1 installation on the server and it all runs smoothly until the end when the following error is displayed.

After the requisite reboot, the following error logs appear in the System event log.
Event ID: 7009 “Timeout (30000 milliseconds) waiting for the SQL Server Integration Services service to connect.”
followed immediately by
Event ID: 7000 “The SQL Server Integration Services service failed to start due to the following error: The service did not respond to the start or control request in a timely fashion.”
Manual attempts to start the service result in an error dialog appearing with “Could not start the SQL Server Integration Services service on Local Computer. Error 1053: The service did not respond to the start or control request in a timely fashion.”
The cause of this issue in my case is that I am installing SQL behind a corporate firewall and the server has no outbound Internet access. This prevents the call to the CryptoAPI checking the Certificate Revocation List at crl.microsoft.com which it does for the SQL Server assembly files. The long delay while the check is being attempted causes the Service Control Manager to report the SSIS service is taking too long to start and the service does not start.
To fix this problem, you need to look at knowledge base article 918222 and install in the correct documented sequence, each of the post SP1 hotfixes. After a reboot at the end of this the server is up and the SQL Server Integration Services (SSIS) service is running happily.
Now onto the rest of the TFS dual-server installation 
Links:
KB Article 918644, “FIX: The SQL Server Integration Services (SSIS) service does not start when you install SQL Server 2005 SP1 on a computer that is already running the SSIS service“.
KB Article 918222, “Cumulative hotfix package (build 2153) for SQL Server 2005 is available“