What Does This Error Mean???

Trying 2 access my email (on live.com, as I always have).  This is what I get:Microsoft.Exchange.Clients.Security.LiveConfigurationHRESULTException: LiveId authentication code has returned error 0x8004920a, indicating that there is a problem with your server configuration. Please check the Application Event Log for detailed information and correct the problem. ---> System.Runtime.InteropServices.COMException (0x8004920A): Certificate cannot be found. Certificate required for the operation cannot be found. at Microsoft.Passport.RPS.Native.IRPSHttpAuth.AuthenticateRawHttp(String siteName, String httpVerb, String path, String QS, String httpVersion, Boolean bHTTPs, String httpHeaders, String httpBody, Object pAuthResultsBag) at Microsoft.Passport.RPS.RPSHttpAuth.Authenticate(String siteName, HttpRequest request, RPSPropBag propBag) at Microsoft.Exchange.Clients.Security.LiveIdAuthentication.Authenticate(HttpContext httpContext, String siteName, String& puid, String& cid, String& membername, UInt32& issueTime, String& responseHeaders, String& redirectUrl, Boolean& hasAcceptedAccrual, UInt32& rpsAuthState) --- End of inner exception stack trace --- at Microsoft.Exchange.Clients.Security.LiveIdErrorHandler.ThrowRPSException(COMException e) at Microsoft.Exchange.Clients.Security.LiveIdAuthentication.Authenticate(HttpContext httpContext, String siteName, String& puid, String& cid, String& membername, UInt32& issueTime, String& responseHeaders, String& redirectUrl, Boolean& hasAcceptedAccrual, UInt32& rpsAuthState) at Microsoft.Exchange.Clients.Security.LiveIdAuthenticationModule.OnAuthenticateRequest(Object source, EventArgs e) Never seen anything like this.  I know it's not their website, b/c I can access it on my phone.....and I DID go back & make sure I logged out, on my ph. Thanks 4 ur help