According to OTN the entry for JDev home should be in the form -
and this applies to Windows as well
so don't just cut and paste the directory path from Windows explorer.
# Master Ant properties file for Fusion Order Demo
# All build files refer to this master list of properties
# Continuous builds override these settings
# $Id: build.properties 812 2007-02-20 07:14:33Z lmunsing $
# Base Directory for library lookup