WCF Mex end point error

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Apologies for cross posting to couple of WCF related forums, but I am
frantically trying to find a solution to this WCF Mex endpoint problem
described below:

I am getting this weird error when trying to invoke an IIS 7.0 (Vista)
hosted WCF Service's mex endpoint using IE browser, usually it should respond
back with the WSDL displayed in IE.
However, I am getting a 400 response error from IIS. Digging into the WCF
tracefile the source of error seems to be invalid XML (see below), since i
am using standard metadata bindings and contract this should work.

I can successfully invoke the service using .svc page and can even get to
the WSDL using https://localhost/ZSTS/STSService?wsdl URL without any error,
it is the https://localhost/ZSTS/STSService/mex endpoint that is giving me
400 error.
I can connect to the service using aspx client as well. Everything works
except the /mex endpoint.

Error stack below:

This is an Active STS Service using Geneva framework and everything is
working fine except the mex endpoint access.

I get same results when using code or web.config file.


<Exception>
<ExceptionType>System.ServiceModel.ProtocolException, System.ServiceModel,
Version=3.0.0.0, Culture=neutral,
PublicKeyToken=b77a5c561934e089</ExceptionType>
<Message>There is a problem with the XML that was received from the network.
See inner exception for more details.</Message>
<StackTrace>
at System.ServiceModel.Channels.HttpRequestContext.CreateMessage()
at
System.ServiceModel.Channels.HttpChannelListener.HttpContextReceived(HttpRequestContext context, ItemDequeuedCallback callback)
at
System.ServiceModel.Activation.HostedHttpTransportManager.HttpContextReceived(HostedHttpRequestAsyncResult result)
at System.ServiceModel.Activation.HostedHttpRequestAsyncResult.HandleRequest()
at System.ServiceModel.Activation.HostedHttpRequestAsyncResult.BeginRequest()
at
System.ServiceModel.Activation.HostedHttpRequestAsyncResult.OnBeginRequest(Object state)
at
System.ServiceModel.Channels.IOThreadScheduler.CriticalHelper.WorkItem.Invoke2()
at
System.ServiceModel.Channels.IOThreadScheduler.CriticalHelper.WorkItem.Invoke()
at
System.ServiceModel.Channels.IOThreadScheduler.CriticalHelper.ProcessCallbacks()
at
System.ServiceModel.Channels.IOThreadScheduler.CriticalHelper.CompletionCallback(Object state)
at
System.ServiceModel.Channels.IOThreadScheduler.CriticalHelper.ScheduledOverlapped.IOCallback(UInt32
errorCode, UInt32 numBytes, NativeOverlapped* nativeOverlapped)
at
System.ServiceModel.Diagnostics.Utility.IOCompletionThunk.UnhandledExceptionFrame(UInt32 error, UInt32 bytesRead, NativeOverlapped* nativeOverlapped)
at System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32
errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP)
</StackTrace>
<ExceptionString>System.ServiceModel.ProtocolException: There is a problem
with the XML that was received from the network. See inner exception for more
details. ---> System.Xml.XmlException: The body of the message cannot be read
because it is empty.
--- End of inner exception stack trace ---</ExceptionString>
<InnerException>
<ExceptionType>System.Xml.XmlException, System.Xml, Version=2.0.0.0,
Culture=neutral, PublicKeyToken=b77a5c561934e089</ExceptionType>
<Message>The body of the message cannot be read because it is empty.</Message>


Any thoughts on what is causing this issue or how to fix it will be of great
help.

thanks

.