There are several python scripts that will do this. Got this one from RDNA in a thread by SVDL:

# ZeroMorphs.py

import TkinterWarning
proceed = TkinterWarning.warn("This script will set all morphs of the currently selected.n"
+"figure to zero, includnig full body morphs.n"
+"Do you wish to proceed?", poser.Language())

if(not proceed):
raise("Script canceled")

scene=poser.Scene()
fig=scene.CurrentFigure()
for act in fig.Actors():
for parm in act.Parameters():
if (parm.IsMorphTarget()==1) or (parm.IsValueParameter()==1):
parm.SetValue(0)

Just cut that and paste it into a text file and name it ZeroMorphs.py and put it in your PythonPoserScriptsScriptsMenuZeroMorphs directory or wherever and you can run it til your hearts content.