update plugin in crm 2011

hi everyone,

i create a plugin which is succesfully work on create event and i want also work this plugin when the entity is update.

i have created a new step and choose update(pre operation mode) and i give orders to these two event.

1-create record.(it works on create event post operation mode)

2-update record. (pre operation mode)

when i try to create or update a record it gives error. business process error.

errror log below

Unhandled Exception: System.ServiceModel.FaultException`1[[Microsoft.Xrm.Sdk.OrganizationServiceFault, Microsoft.Xrm.Sdk, Version=5.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]: The given key was not present in the dictionary.Detail:
<OrganizationServiceFault xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.microsoft.com/xrm/2011/Contracts">
  <ErrorCode>-2147220891</ErrorCode>
  <ErrorDetails xmlns:d2p1="http://schemas.datacontract.org/2004/07/System.Collections.Generic">
    <KeyValuePairOfstringanyType>
      <d2p1:key>CallStack</d2p1:key>
      <d2p1:value xmlns:d4p1="http://www.w3.org/2001/XMLSchema" i:type="d4p1:string">   at Microsoft.Crm.Extensibility.VersionedPluginProxyStepBase.Execute(PipelineExecutionContext context)
   at Microsoft.Crm.Extensibility.Pipeline.Execute(PipelineExecutionContext context)
   at Microsoft.Crm.Extensibility.MessageProcessor.Execute(PipelineExecutionContext context)
   at Microsoft.Crm.Extensibility.InternalMessageDispatcher.Execute(PipelineExecutionContext context)
   at Microsoft.Crm.Extensibility.ExternalMessageDispatcher.ExecuteInternal(IInProcessOrganizationServiceFactory serviceFactory, IPlatformMessageDispatcherFactory dispatcherFactory, String messageName, String requestName, Int32 primaryObjectTypeCode, Int32 secondaryObjectTypeCode, ParameterCollection fields, CorrelationToken correlationToken, CallerOriginToken originToken, UserAuth userAuth, Guid callerId, Guid transactionContextId, Int32 invocationSource, Nullable`1 requestId, Version endpointVersion)
   at Microsoft.Crm.Extensibility.OrganizationSdkServiceInternal.ExecuteRequest(OrganizationRequest request, CorrelationToken correlationToken, CallerOriginToken callerOriginToken, WebServiceType serviceType, UserAuth userAuth, Guid targetUserId, Boolean traceRequest, OrganizationContext context, Boolean returnResponse)
   at Microsoft.Crm.Extensibility.OrganizationSdkServiceInternal.ExecuteRequest(OrganizationRequest request, CorrelationToken correlationToken, CallerOriginToken callerOriginToken, WebServiceType serviceType)
   at Microsoft.Crm.Extensibility.OrganizationSdkServiceInternal.Execute(OrganizationRequest request, CorrelationToken correlationToken, CallerOriginToken callerOriginToken, WebServiceType serviceType)</d2p1:value>
    </KeyValuePairOfstringanyType>
    <KeyValuePairOfstringanyType>
      <d2p1:key>OperationStatus</d2p1:key>
      <d2p1:value xmlns:d4p1="http://www.w3.org/2001/XMLSchema" i:type="d4p1:string">0</d2p1:value>
    </KeyValuePairOfstringanyType>
  </ErrorDetails>
  <Message>The given key was not present in the dictionary.</Message>
  <Timestamp>2013-03-08T12:51:56.8386763Z</Timestamp>
  <InnerFault i:nil="true" />
  <TraceText>

[SamplePlugins: Plug_ins.AccountNumberPlugin]
[73ac7895-ed87-e211-9646-00505683000f: Plug_ins.AccountNumberPlugin: Update of new_operationscorecard]


</TraceText>
</OrganizationServiceFault>

Crm Software Specialist