Problem with plugin registration

hello,

i'm upgraded my CRM from v4 to 2011 and after this every plugins working fine.

but i could not register one of that plugins on new organization.

when i choose plugin in pluginregistration.exe,

this error shown:

Unhandled Exception: System.IO.FileLoadException: Could not load file or assembly 'Microsoft.Crm.Sdk, Version=5.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)
   at System.ModuleHandle.ResolveType(Int32 typeToken, RuntimeTypeHandle* typeInstArgs, Int32 typeInstCount, RuntimeTypeHandle* methodInstArgs, Int32 methodInstCount)
   at System.ModuleHandle.ResolveTypeHandle(Int32 typeToken, RuntimeTypeHandle[] typeInstantiationContext, RuntimeTypeHandle[] methodInstantiationContext)
   at System.Reflection.Module.ResolveType(Int32 metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments)
   at System.Reflection.CustomAttribute.FilterCustomAttributeRecord(CustomAttributeRecord caRecord, MetadataImport scope, Assembly& lastAptcaOkAssembly, Module decoratedModule, MetadataToken decoratedToken, RuntimeType attributeFilterType, Boolean mustBeInheritable, Object[] attributes, IList derivedAttributes, RuntimeType& attributeType, RuntimeMethodHandle& ctor, Boolean& ctorHasParameters, Boolean& isVarArg)
   at System.Reflection.CustomAttribute.GetCustomAttributes(Module decoratedModule, Int32 decoratedMetadataToken, Int32 pcaCount, RuntimeType attributeFilterType, Boolean mustBeInheritable, IList derivedAttributes)
   at System.Reflection.CustomAttribute.GetCustomAttributes(RuntimeType type, RuntimeType caType, Boolean inherit)
   at PluginRegistrationTool.AssemblyReader.RetrievePluginsFromAssembly(String path)
   at PluginRegistrationTool.AssemblyReader.RetrievePluginsFromAssembly(String path)
   at PluginRegistrationTool.RegistrationHelper.RetrievePluginsFromAssembly(String pathToAssembly)
   at PluginRegistrationTool.PluginRegistrationForm.btnLoadAssembly_Click(Object sender, EventArgs e)

please help me to fix this problem.

thank's.