Another Problem installing Grasshopper in Rhino 5 WIP 64-bit

I took a look around the discussions and I wasn't able to find the exact problem that I'm having. I followed all the advice and instructions to install GH in Rhino 5 64-bit, but I continue to get this error when dragging & dropping GrasshopperPlugin.rhp from the Rhino 4 plugins directory into Rhino 5's window:

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Rhinoceros 4.0  Rhino.NET Error

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Exception occured in plug-in Grasshopper

Method not found: 'Void Rhino.Runtime.HostUtils.InitializeRhinoCommon()'.

Stack trace:

   at Grasshopper.Plugin.GH_PluginUtil.LoadGrasshopper()

   at GrasshopperPlugin.GrasshopperPlugin.OnLoadPlugIn()

   at RhDN_NativePlugInBase<CRhinoUtilityPlugIn,RMA::Rhino::MRhinoUtilityPlugIn>.OnLoadPlugIn(RhDN_NativePlugInBase<CRhinoUtilityPlugIn\,RMA::Rhino::MRhinoUtilityPlugIn>* )

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After that, I get the same error as others which states that the 64-bit plugin can't be run.

Any help would be appreciated!