Unable to verify the printer on the network

Hi,

I have a home IP network with an HP4100N network laser-printer connected via JetDirect card to a powerline device and then to a hub.

Up until recently, all computers on my network could successfully print to the printer via the JetDirect card and IP (192.168.0.100).

HOWEVER, my girlfriends MacBook Pro running Mac OX 10.9.5 suddenly stopped printing to the printer and things were just starting to build up in the print queue. The printer continues to print normally for everyone else on Mac and even a Windows 7 machine, eeek! 😉

Turning the printer on and off a couple of times, resetting the network etc, I then finally deleted the print queue and tried to setup a new connection to the printer again on her computer via the prefs and the IP JetDirect socket option (like I have done on all the other computers).

When I enter the printer IP address into the Mac Printer & Scanners settings, Mac OS tried to interrogate printer model etc and it comes back with a Generic Postscript Printer profile and not the HP specific one. (Again, every other computer can setup fine at this point!)

On her computer, when you try and install the printer with the wrong profile (or even the correct one if manually chosen), it eventually says:

'Unable to verify the printer on your network'.

Network utility:

I then tried using the Network Utility to ping the printer from my laptop, this works.

I tried to ping the printer from her computer, this doesn't work and it times out!

then...

I tried pinging her MBP from my MBP and this works. Then I pinged my MBP from her MBP, this works.

So her computer is on the network, but is not able to see the printer.

I then hard- IP'd a new IP address on the printer (just to rule this out), setup all the computers to this new printer, all worked well except for her computer, which once again couldn't see the printer. (I can't ping to it either again from her computer, even with the new IP!)

I think I've tried all the obvious things, updating software, resetting things, turning the firewall off completely....but all to no avail.

The problem, it seems to me, is with her MBP rather than with the network or the printer (as all other computers can print!).

So...the million dollar question is... Can anyone tell me what is going on?! How do I get her computer to print to this printer again??

thanks very much.