This is a hot topic discussed in the forums and we have decided to put this on a knowledge base article:
Web services may fail on Microsoft Internet Information Services (IIS) 7.5 and Windows 7 Service Pack 1 with .NET Framework 4.0 due to extensionless URL handlers
Here is the symptoms you may see:
Consider the following scenario. You have a Microsoft Windows 7 server running Microsoft Internet Information Services (IIS) and the .NET Framework 4.0. Your IIS web applications host web services (for example .asmx or WCF-based services) or JSON web services using .aspx page methods. You install Service Pack 1 for Windows 7. After installing the service pack, your web applications may begin to suffer from undesirable or unexpected behavior including (but not limited to):
- Additional internal server-side requests are issued to serve the requested resource. The requested resource is eventually served to the client as expected.
- The web service processing fails and the application returns an error to the client, or other similar unexpected behavior occurs.
For more details please read the KB article.
Web Services, .NET 4.0, IIS 7.5, IIS 7.0