HP 6940 offline

I have a netgear router with the HP printer attached via a cable to port number 4 (networked). About half of the time when I want to print, the printer shows it is offline even though it is not. I can ping it successfully from a console, I can see it if I sign on to the netgear via a web browser and look at attached devices. My PC is 192.168.1.2, printer is 192.168.1.3, laptop is 192.168.1.4. Printer device name is HP0017A46B5AOB.
I also have a laptop which attaches via wireless to the same router. I never have a problem with the printer access from that laptop.
When the problem occurs, I have to "add printer" to be able to print. This installs copy 2, etc of the printer. I left some of the old installations in place and they never show ready, always offline. I have tried using the original CD to install as well as the built in VISTA drivers, both give the same results.
I have done an upgrade of the netgear software to no avail.
I have not been able to pin down what makes the problem appear. It seams to be random.

This is very, very frustrating. Please help.

Just to make sure you have all of the info - I have:
HP Pavillion 6560z and Vista home premium. Printer sharing is not turned on. Printer is set up to spool documents (default). WGR614 netgear router with version 7 software.

Since I got no response here, I searched for about 20 sites and found this one. Deskjet 6940 keeps going offline - HP Support Forum It has a manual way to install the printer. I did that and will see if that helps. This post is for others who may have the same problem.