More stuff on WCF / IIS7 - IIS7 has got some funky new tracing features built in to diagnose failed requests. Again, this is not enabled by default; you need to go into "Turn Windows Features on or off" and select "Interet Information Services\World Wide Web Services\Health and Diagnostics\Tracing". Once done, you'll see a new entry in the IIS admin tool - select your web site and on the Actions pane you can now configure the failed request tracing. Enjoy!