So I got the exact same problem and I followed your instructions (thanks!)...
I disabled the http module in my child web config...
and now I get the following error (great!)...
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Configuration Error
Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately.
Parser Error Message: Could not load file or assembly 'umbraco' or one of its dependencies. The system cannot find the file specified.
Source Error:
Line 66: <add verb="GET,HEAD" path="ScriptResource.axd" type="System.Web.Handlers.ScriptResourceHandler, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
Line 67: <!-- UMBRACO CHANNELS -->
Line 68: <add verb="*" path="umbraco/channels.aspx" type="umbraco.presentation.channels.api, umbraco"/>
Line 69: <add verb="*" path="umbraco/channels/word.aspx" type="umbraco.presentation.channels.wordApi, umbraco"/>
Line 70: </httpHandlers>
Source File: C:\Inetpub\wwwroot\NaturalSolutions\web.config Line: 68
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Help!!!