An error occured while connecting to CRM server within my plug-in - plugins

Question

Please help me figure out how to get ride of this error:
An error occured while connecting to CRM server.
My code
namespace AutoCreateAccountAndContactFromLead
{
public class CreateAccountAndContact : IPlugin
{
public void Execute(IServiceProvider serviceProvider)
{
// Extract the tracing service for use in debuuging sandboxed plug-ins
ITracingService tracingService = (ITracingService)serviceProvider.GetService(typeof(ITracingService));
IPluginExecutionContext context = (IPluginExecutionContext)serviceProvider.GetService(typeof(IPluginExecutionContext));
// The InputParamaters collection contains all the data passed in the message request.
if(context.InputParameters.Contains("Target") && context.InputParameters["Target"] is Entity)
{
// Obtain the target entity from the input parameter
Entity lead = (Entity)context.InputParameters["Target"];
// If the entity's schema name is not "lead", then return. If it is, execute try block.
if (lead.LogicalName != "lead")
return;
try
{
// check plug-in is registerd in pre-operational stage.
if (context.Stage == 20)
{
// vars for create contact
var firstName = lead.Attributes["firstname"];
var lastName = lead.Attributes["lastname"];
var jobtitle = lead.Attributes["jobtitle"];
var emailaddress1 = lead.Attributes["emailaddress1"];
var mobilephone = lead.Attributes["mobilephone"];
var businessphone = lead.Attributes["telephone1"];
// vars for create account
var accountname = lead.Attributes["companyname"];
var websiteurl = lead.Attributes["websiteurl"];
var street1 = lead.Attributes["address1_line1"];
var street2 = lead.Attributes["address1_line2"];
var street3 = lead.Attributes["address1_line3"];
var city = lead.Attributes["address1_city"];
var stateprovice = lead.Attributes["address1_stateorprovince"];
var postalcode = lead.Attributes["address1_postalcode"];
var countryregion = lead.Attributes["address1_country"];
// create a contact entity
Entity contact = new Entity("contact");
contact["firstname"] = firstName;
contact["lastname"] = lastName;
contact["jobtitle"] = jobtitle;
contact["emailaddress1"] = emailaddress1;
contact["telephone1"] = businessphone;
contact["emailaddress1"] = emailaddress1;
contact["mobilephone"] = mobilephone;
// create an account entity
Entity account = new Entity("account");
account["name"] = accountname;
account["websiteurl"] = websiteurl;
account["address1_line1"] = street1;
account["address1_line2"] = street2;
account["address1_line3"] = street3;
account["address1_city"] = city;
account["address1_stateorprovince"] = stateprovice;
account["address1_postalcode"] = postalcode;
account["address1_country"] = countryregion;
// Obtain the orginxation service reference.
IOrganizationServiceFactory serviceFactory = (IOrganizationServiceFactory)serviceProvider.GetService(typeof(IOrganizationServiceFactory));
IOrganizationService service = serviceFactory.CreateOrganizationService(context.UserId);
// contact and account
service.Create(contact);
service.Create(account);
}
}
catch (FaultException<OrganizationServiceFault> ex)
{
throw new InvalidPluginExecutionException("An error occured while connecting to CRM server.", ex);
}
catch (Exception ex)
{
tracingService.Trace("FollowupPlugin: {0}", ex.ToString());
throw;
}
}
}
}
}