"socket operation" exception with PayPal express

Hi,

I'm hoping someone can help with the following problem:

PayPal Express works perfectly fine locally, but abends in the production site upon clicking the PayPal icon. There is no difference other than localhost vs. production, all settings exactly the same.

The error message is as follows:

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A socket operation was attempted to an unreachable network 66.211.168.126:443

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Net.Sockets.SocketException: A socket operation was attempted to an unreachable network 66.211.168.126:443

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[SocketException (0x2743): A socket operation was attempted to an unreachable network 66.211.168.126:443]
   System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress) +239
   System.Net.Sockets.Socket.InternalConnect(EndPoint remoteEP) +35
   System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Int32 timeout, Exception& exception) +224

[WebException: Unable to connect to the remote server]
   System.Net.HttpWebRequest.GetRequestStream() +5322142
   System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters) +103
   NopSolutions.NopCommerce.Payment.Methods.PayPal.PayPalSvc.PayPalAPIAASoapBinding.SetExpressCheckout(SetExpressCheckoutReq SetExpressCheckoutReq) in Reference.cs:1016
   NopSolutions.NopCommerce.Payment.Methods.PayPal.PayPalExpressPaymentProcessor.SetExpressCheckout(Decimal OrderTotal, String ReturnURL, String CancelURL) in PayPalExpressPaymentProcessor.cs:215
   NopSolutions.NopCommerce.Web.Modules.PaypalExpressButton.btnPaypalExpress_Click(Object sender, EventArgs e) in PaypalExpressButton.ascx.cs:82
   System.Web.UI.ImageClickEventHandler.Invoke(Object sender, ImageClickEventArgs e) +0
   System.Web.UI.WebControls.ImageButton.OnClick(ImageClickEventArgs e) +108
   System.Web.UI.WebControls.ImageButton.RaisePostBackEvent(String eventArgument) +118
   System.Web.UI.WebControls.ImageButton.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1565
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