unable to load grasshopper

hello, any idea what might be the problem when loading freshly installed grasshopper? i am using rhino 4 sr9. grasshopper does not start>

Command: Grasshopper
Rhino.NET plug-in: C:\Program Files\Rhinoceros 4.0\Plug-ins\Grasshopper\GrasshopperPlugin.rhp
- referenced assembly count: 5
- Rhino_DotNet
- mscorlib
- System.Windows.Forms
- Grasshopper
- System
- plug-in passes RhinoDot_NET.DLL reference version check
- loading assembly using Reflection::Assembly::LoadFrom
- attempting to find definition of MRhinoPlugInAttributes subclass
- 12 exported types
Rhino.NET successfully loaded C:\Program Files\Rhinoceros 4.0\Plug-ins\Grasshopper\GrasshopperPlugin.rhp

Unable to load GrasshopperPlugin.rhp plug-in: application initialization failed.
Unknown command: Grasshopper

i was using rhino 4 sr7 and grasshopper 0.6 until now with no problems. any help please?

s.