The request failed with HTTP Status 405: Method Not Allowed.

Note: This is KB article is taken from MSDN as it is for my own reference.

If you are getting error when accessing a Web Service, 'The request failed with HTTP Status 405: Method Not Allowed', cause may be any one of this listing.

1. First thing, you want to check is WebService is being accessible from the browser using the URL (.wsdl or asmx).
2. Bayer White talks about his experience with "Method Not Allowed" on Project Server:
   
3. One guy suggested this on Microsoft forums:
   
   Just got this message today after installing our web services on a virgin box. For us, the problem was apparently the method we used to set up the server, and the order in which we installed components. You may need to run the aspnet_regiis.exe program, which is located in \WINNT\Microsoft.NET\Framework\v1.1.4322.
   
   Use the /? option to find the command line parameters from the dos prompt. We did the /i option to install 1.1.4322.
    
4. Here is something related to machine.config and HttpGet and HttpPost:

PDSTest.NET Related Error:

'The request failed with HTTP Status 405: Method Not Allowed' Error

When you use the PDSTest.NET tool and you run a PDS query against a URL where the virtual directory name is not "ProjectServer," you may receive the following error message:

PDSTest.NET Exception Occurred while processing the request.
The request failed with HTTP Status 405: Method Not Allowed

This behavior occurs when you use the EditSite tool to create additional virtual directories in Project Server 2003. In this case, the .wsdl file may not be mapped correctly in Microsoft Internet Information Services (IIS).
To download and to install the Project Server 2003 EditSite tool, visit the following Microsoft Web site: http://www.microsoft.com/downloads/details.aspx?FamilyID=6dc2c83e-54e1-40a9-9bb8-2dd293226b6f&DisplayLang=en (http://www.microsoft.com/downloads/details.aspx?FamilyID=6dc2c83e-54e1-40a9-9bb8-2dd293226b6f&DisplayLang=en)

To resolve this problem, map the .wsdl application extension to the correct file in IIS. To do this, follow these steps:

1.	Log on to the computer that is running Project Server 2003 by using an account that has administrative permissions.
2.	Click Start, point to Administrative Tools, and then click Internet Information Services (IIS) Manager.
3.	In the Internet Information Services (IIS) Manager MMC snap-in, expand ServerName, expand Web sites, expand Default Web site, right-click ProjectServer, and then click Properties.
4.	In the ProjectServer Properties box, click the Virtual Directory tab, and then click Configuration.
5.	In the Application Configuration box, click the Mappings tab, select .wsdl under Application Extensions, and then click Edit.
6.	In the Add/Edit Application Extension Mapping box, click Browse.
7.	In the Open box, locate the Program Files\Common Files\MSSOAP\BINARIES\ folder. Then, click SOAPIS30.dll, click Open, and then click OKtwo times.