Can not access ASP.NET Configuration tool

I am so frustrated! I am using IIS7 and Visual Studio 2005 and I can not access the configuration tool this is the error I get:

Server Error in '/asp.netwebadminfiles' Application. -------------------------------------------------------------------------------- Unable to serialize the session state. In 'StateServer' and 'SQLServer' mode, ASP.NET will serialize the session state objects, and as a result non-serializable objects or MarshalByRef objects are not permitted. The same restriction applies if similar serialization is done by the custom session state store in 'Custom' mode.


Please HELP

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