WORKFLOW in waiting status crm 4.0

Hi,

I have created a custom workflow but it crash and i don't know why exactly.

Here is trace file :

# CRM Tracing Version 2.0
# LocalTime: 2013-04-05 10:27:02.4
# Categories: *:Error
# CallStackOn: Yes
# CRMVersion: 4.0.7333.1316
# DeploymentType: OnPremise
# ScaleGroup:
# ServerRole: AppServer, AsyncService, DiscoveryService, WebService, ApiServer, HelpServer, DeploymentService

[2013-04-05 10:27:02.4] Process:CrmAsyncService |Organization:c768df67-4ac0-4975-9c0a-462a721c52b5 |Thread:   10 |Category: Platform.Workflow |User: 00000000-0000-0000-0000-000000000000 |Level: Error | WorkflowHost.OnWorkflowTerminated
at WorkflowHost.OnWorkflowTerminated(Object sender, WorkflowTerminatedEventArgs args)
at WorkflowRuntime.OnScheduleTerminated(WorkflowExecutor schedule, WorkflowTerminatedEventArgs args)
at WorkflowRuntime.WorkflowExecutionEvent(Object sender, WorkflowExecutionEventArgs e)
at EventHandler`1.Invoke(Object sender, TEventArgs e)
at WorkflowExecutor.FireWorkflowTerminated(Exception exception)
at SchedulerLockGuard.FireEvents(List`1 eventList, WorkflowExecutor workflowExec)
at SchedulerLockGuard.Dispose()
at WorkflowExecutor.RunSome(Object ignored)
at WorkItem.Invoke(WorkflowSchedulerService service)
at DefaultWorkflowSchedulerService.QueueWorkerProcess(Object state)
at _ThreadPoolWaitCallback.WaitCallback_Context(Object state)
at ExecutionContext.runTryCode(Object userData)
at RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData)
at ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
at ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at _ThreadPoolWaitCallback.PerformWaitCallbackInternal(_ThreadPoolWaitCallback tpWaitCallBack)
at _ThreadPoolWaitCallback.PerformWaitCallback(Object state)
>Workflow terminated: {64C52591-CA9D-E211-9514-001E0BBD9F2E} - System.NullReferenceException: La référence d'objet n'est pas définie à une instance d'un objet.
   à Datasurf.Crm.Data.datasurf_create_oit_create_campaign_oas.datasurf_create_oit_create_campaign_oas.Execute(IWorkflowContext ctx, String fonction, String connexionString, String accountid, String user, String password, String proxy, String entityname)
   à WF_datasurf_oit_create_campaign_crm.datasurf_oit_create_campaign_oas.Execute(ActivityExecutionContext executionContext)
   à System.Workflow.ComponentModel.ActivityExecutor`1.Execute(T activity, ActivityExecutionContext executionContext)
   à System.Workflow.ComponentModel.CompositeActivityExecutor`1.Execute(T activity, ActivityExecutionContext executionContext)
   à System.Workflow.ComponentModel.ActivityExecutor`1.Execute(Activity activity, ActivityExecutionContext executionContext)
   à System.Workflow.ComponentModel.ActivityExecutionFilter.Execute(Activity activity, ActivityExecutionContext executionContext)
   à System.Workflow.ComponentModel.FaultAndCancellationHandlingFilter.Execute(Activity activity, ActivityExecutionContext executionContext)
   à System.Workflow.ComponentModel.ActivityExecutorOperation.Run(IWorkflowCoreRuntime workflowCoreRuntime)
   à System.Workflow.Runtime.Scheduler.Run()

Thank you for any answer.