I created a WCF restfull service in .NET 4 and I published it under IIS 7.5/windows 7 x86. The verbs GET and POST worked fine, but the DELETE and PUT gave an error:
You don't need to remove module for whole site. You can configure modules per application. Modules section is available in Management console per application.
You really have to remove WebDav for REST service's application because PUT and DELETE verbs were formerly defined for WebDav and are consumed by WebDav automatically.