More good articles on framework installation issues by Aaron Stebner are available than the ones related to the verification and cleanup tools I posted about last week. Here's a quick selection of a few of the articles about WCF.
The first article covers how to diagnose issues with ServiceModelReg, which is the command line tool run during setup that is responsible for updating the WCF configuration with IIS. There's also a specific diagnosis for solving issues related to the temporary files used by ServiceModelReg. If this advice doesn't help work out the problem, it's often useful to try the most recent version of the framework in case the setup issue is resolved by improvements to the installation logic. There are several cases where installing Orcas SP1 instead of an earlier version of WCF can workaround setup failures with earlier framework versions due to a more robust installer. Finally, as a last resort you may want to check out the general advice in the framework troubleshooting guide for diagnosing and resolving issues.