CRM 2013 : ActivityFeeds.Plugins.ActivityClose: Create of account

Hello,

When i'm trying to save an account or a custom entity call "new_chantier" i got a SDK error.
I activated trace:

>Web Service Plug-in failed in SdkMessageProcessingStepId: {886AED7E-489A-E411-82AE-000C29BAC811}; EntityName: 
account; Stage: 40; MessageName: Create; AssemblyName: ActivityFeeds.Plugins.ActivityClose, 
ActivityFeeds.Plugins, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35; 
ClassName: ActivityFeeds.Plugins.ActivityClose; Exception: Unhandled Exception: 
Microsoft.Xrm.Sdk.InvalidPluginExecutionException: An error occurred. Contact a system administrator or 
refer to the Microsoft Dynamics CRM SDK troubleshooting guide.
   at ActivityFeeds.Plugins.PluginBase`1.Execute(IServiceProvider serviceProvider)
   at Microsoft.Crm.Extensibility.V5PluginProxyStep.ExecuteInternal(PipelineExecutionContext context)
   at Microsoft.Crm.Extensibility.VersionedPluginProxyStepBase.Execute(PipelineExecutionContext context)

I lauch plugin registrator and disable the step, then it works.

What's happening ? I guess if this plugin exist, it must be enabled

Thank you in advance
Regards,