I was breaking my head trying to solve it in Python, but was easier solving it in Aspen renaming the node. I've noticed, also, that spaces give problems too, so should be renamed as well. In some cases it can't be done or I don't know how, for example:
MW = aspen.Tree.FindNode("\\Data\\Properties\\Parameters\\Pure Components\\REVIEW1\\Input\\VALUE\\MW ACID")
It returns a none object, but I figured out a tricky way to get the value:
MW = aspen.Tree.FindNode("\\Data\\Properties\\Parameters\\Pure Components\\REVIEW1\\Input\\VALUE")
for o in MW.Elements:
if o.Name == "MW ACID":
MW_acid = o.Value
I think that ActiveX automation is not perfect implemented yet, or was not though for Python.