The request filtering module is configured to deny a request that exceeds the request content length

SUMMARY

This problem occurs because by default in IIS 7 enabled requestFiltering that have MaxAllowedContentLength property. It specifies, in bytes, the maximum length of content in a request. The default is 30000000 (approximately 30 megabytes.)

SOLUTION

To change this value you must include following code in your Web.config file if you want to apply this setting only to you application. If you want to change this setting for all of the computer and not just this ASP.NET application, you must modify the Machine.config file. By default, the element is set to the following parameters in the Machine.config file: The Machine.config file is located in the \System Root\Microsoft.NET\Framework\Version Number\CONFIG directory.

<configuration>
   <system.webServer>
      <security>
         <requestFiltering>
            <requestLimits maxAllowedContentLength="100000000"/> 
         </requestFiltering>
      </security>
   </system.webServer>
</configuration>      

REFERENCES

Microsoft Developer Network:
http://msdn2.microsoft.com/en-us/library/ms689462.aspx