CrmSvcUtil.exe Secirity Error

I am new to Dynamics CRM. iam try to generate the proxy class using CrmSvcUtil.exe

this is my command

CrmSvcUtil.exe /codeCustomization:"Microsoft.Xrm.Client.CodeGeneration.CodeCustomization,Microsoft.Xrm.Client.CodeGeneration" /out:E:\Xrm.cs /url:https://mdtestuser.crm5.dynamics.com/XRMServices/2011/Organization.svc /domain:mdtestuser /username:"MDTest@MDTestUser.onmicrosoft.com" /password:"PASSWORD" /namespace:Xrm /serviceContextName:XrmServiceContext

but i am return an error says ;

Exiting program with exception: An error occurred when verifying security for the message.
Enable tracing and view the trace files for more information.
CrmSvcUtil.exe Error: 0 : Exiting program with exit code 2 due to exception : Sy
stem.ServiceModel.FaultException: An error occurred when verifying security for
the message.

both my CRM 2011 server and client computer in same timezone. please help me to resolve this issue ASAP.

Gimhan