While trying to use x4juli with groovy I recognize that the second JVM property is not used as expected.
To reproduce the problem you can try the following script with Ubuntu (maybe also applicable with other Linux versions):
groovy -Djava.foo=test -Djava.bar -e "println System.getProperty('java.foo'); println System.getProperty('java.bar');"
Script will end with
Caught: java.io.FileNotFoundException: /export/home/marcel/java.bar (/export/home/marcel/java.bar)
I tested this also with Windows Vista where it works as expected.