http 500.0.64 IIS with Client Certificate Required

Hi All,

* We have IIS7, ARR configured for website, SSL + Client Certificate Required.

* This setup is running fine with many partners, but only for 1 partner we are getting below error into our IIS logs.

016-02-22 12:53:25 194.16.174.71 POST /MySecureSite/BTSHTTPReceive.dll - 443 - 194.16.174.96 GIS/PsHttpClientAdapter 500 0 64 109

HTTP Error :  500.0.64 

We already verified Client certificate's CA is already in "Trusted Root Certificate Authority".

And also verified   MS KB977377 is not applied to server.

Even we added following registry entry and restarted the Server.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\DisableRenegoOnServer to 0

But still same error.

Please can anyone help on this.

Thanks in advance.

Regards

Kundan