Sharepoint sandbox error

Hello everybody ! 

I've started coding under Sharepoint system with event receivers, more precisely list item events from document library, with this following code :

public override void ItemAdded(SPItemEventProperties properties)
{
            base.ItemAdded(properties);
            System.Diagnostics.Debug.WriteLine("ItemAdded");
            string url = string.Format("{0}/Shared Documents/Tuteur/NOMDUTUTEUR/{1}", properties.WebUrl, properties.ListItem.File.Name);
            System.Diagnostics.Debug.WriteLine(url);
            properties.ListItem.CopyTo(url); //Problem here
}

I've the error "The sandboxed code execution request was refused because the Sandboxed Code Host Service was too busy to handle the request". I followed this link http://blogs.msdn.com/b/sharepointdev/archive/2011/02/08/error-the-sandboxed-code-execution-request-was-refused-because-the-sandboxed-code-host-service-was-too-busy-to-handle-the-request.aspx but nothing changed.

The system is Sharepoint 2010 under Windows 8, what can I do to solve this problem ?

Thanks in advance.

Best regards.