|Did S-video ever work on either?|
Be sure TV is set to the correct input.
As above check that laptop is correctly set to provide video output.
Be sure we have the correct pin numbers too. 7 or 4 are the two and they are different.
"Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, are in my top 10