try this. select your geometry. go to the hypershade bottom window. click graph>input output connections. the history nodes will be names tweak1, tweak2... and the blenshape nodes will be called blendShape1 or whatever name that you might have given them while creating blendshape.
just select all the history nodes (being careful not to select any blendshape nodes) and delete.
i think this should solve your problem.