Unable to create new WorkflowInstance for WorkflowDefinition while creating shared mailbox

Hi all,

while im trying to create shared amilbox using FIM portal im getting below error.

EXCEPTION DATA
MESSAGE: Unable to create new WorkflowInstance for WorkflowDefinition 'XXXXXXXXXXXXXXXXXXXXXXXX'.
METHOD:System.Exception ThrowException(System.Exception)
METHOD:Void StartWorkflowInstance(System.Guid, System.Collections.Generic.KeyValuePair`2[System.String,System.Object][])
INNER EXCEPTION DATA
MESSAGE: The workflow failed validation.
METHOD:Void ValidateDefinition(System.Workflow.ComponentModel.Activity, Boolean, System.Workflow.ComponentModel.Compiler.ITypeProvider)
METHOD:System.Workflow.ComponentModel.Activity LoadRootActivity(System.String, System.String, Byte[], Boolean, Boolean)
METHOD:System.Workflow.ComponentModel.Activity GetOrGenerateDefinition(System.Type, System.String, System.String, Byte[], Boolean, Boolean ByRef)
METHOD:System.Workflow.ComponentModel.Activity GetRootActivity(System.String, System.String, Boolean, Boolean)
METHOD:System.Workflow.ComponentModel.Activity InitializeExecutor(System.Guid, System.Workflow.Runtime.CreationContext, System.Workflow.Runtime.WorkflowExecutor, System.Workflow.Runtime.WorkflowInstance)
METHOD:System.Workflow.Runtime.WorkflowExecutor Load(System.Guid, System.Workflow.Runtime.CreationContext, System.Workflow.Runtime.WorkflowInstance)
METHOD:System.Workflow.Runtime.WorkflowExecutor GetWorkflowExecutor(System.Guid, System.Workflow.Runtime.CreationContext)
METHOD:System.Workflow.Runtime.WorkflowInstance InternalCreateWorkflow(System.Workflow.Runtime.CreationContext, System.Guid)
METHOD:System.Workflow.Runtime.WorkflowInstance CreateWorkflow(System.Xml.XmlReader, System.Xml.XmlReader, System.Collections.Generic.Dictionary`2[System.String,System.Object], System.Guid)
METHOD:Void StartWorkflowInstance(System.Guid, System.Collections.Generic.KeyValuePair`2[System.String,System.Object][])

Can anybody help please