I seem to run into this often. Thanks a lot HP.
Symptom: NDPS manager cannot communicate with an IP printer, although you can ping it.
Solution: change the gateway line to the following:
NDPSGW PORT=RAW HOSTADDRESS=<printer IP>
instead of
NDPSGW PORT=LPR HOSTADDRESS=<printer IP> PRINTERNAME=ra
It is because of http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?lang=en&cc=us&objectID=c00605333
