500.21 Error for PUT web service calls in Admin

We just moved our website from its dev subdomain to the "live" url on the same Windows 2008 R2 64-bit server with IIS 7.5. Although the public portions of the site function as expected, we now receive the following error message whenever we PUT to a web service in the Sitefinity admin--essentially any attempt to use the admin to update a page, content item, rss or search index, etc. Needless to say, these issues did NOT occur on the dev subdomain on this same server.

ERROR 500.21
Handler "svc-Integrated-4.0" has a bad module "ManagedPipelineHandler" in its module list

Having Googled the 500.21 and the above message, I have already used aspnet_regiis -i to rebuild ASP.NET 4.0.30319 and "repaired" ASP.NET 4 on this server without success. I've also added a machine key to the web.config without success. I've also checked and rechecked IIS settings, permissions, etc.

Since this site's admin worked fine on the dev subdomain, I'm at a loss.  Any suggestions?

UPDATE: For those interested, the solution to this issue was to simply create a new web site within IIS 7.5 on this server. Although the settings, files, etc. for the new site are identical to the original--we copied them--the new site works without issue.  I suppose this is the "clean" installation path that has appeared on many other threads.  Don't know why it was necessary, but it works.

Your <handler> section is probably invalid.

HTTP Error 500.21 - Internal Server Error

Handler "<HANDLER_NAME>" has a bad module "ManagedPipelineHandler" in its module list

You probably have a handler mapping that does not have the correct precondition.  

IIS is not forgiving in regard to typos, and preconditions are case-sensitive.  

The text must be preCondition=”integratedMode” or preCondition=”classicMode”.

1) Check this post for more information: 

blogs.msdn.com/.../iis-7-0-asp-net-pipelines-modules-handlers-and-preconditions.aspx

2) Also, set the preCondition mode of your IsapiModule:

<add name="WildCard" path="*" verb="*" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework64\v4.0.30319\aspnet_isapi.dll" resourceType="Unspecified" requireAccess="None" preCondition="classicMode,runtimeVersionv4.0,bitness64" />

<add name="WildCard32" path="*" verb="*" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework\v4.0.30319\aspnet_isapi.dll" resourceType="Unspecified" requireAccess="None" preCondition="classicMode,runtimeVersionv4.0,bitness32" />