Hi, 

I'm trying to customize a button command in CRM 2011 but I get following error.

Any tip to solve this?

Ribbon Workbench Exception Report:
 Version=1.0.1.9
Type:NullReferenceException
Message:Object reference not set to an instance of an object.
StackTrace:   at Develop1.Xrm.Silverlight.Ribbon.Model.ButtonControlBase.<get_CustomiseCommandCommand>b__21()
   at RelayCommand.Execute(Object parameter)
   at System.Windows.Controls.MenuItem.OnClick()
   at System.Windows.Controls.MenuItem.OnMouseLeftButtonDown(MouseButtonEventArgs e)
   at System.Windows.Controls.Control.OnMouseLeftButtonDown(Control ctrl, EventArgs e)
   at MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, Int32 actualArgsTypeIndex, String eventName, UInt32 flags)