Loaded our internal dev site and received the titled error. Apparently this happens sometimes when running DotNet 3.0 or 3.5 WCF features on a DotNet 4.0 framework.
CSS3 PIE is a .htc file that faithfully recreates css3 styling in early versions of internet explorer. Simply adding "behavior: url(path/to/PIE.htc);" at the end of the selectors scope that contains the CSS3 rule causes it to render correctly in otherwise unsupported versions of IE.