Hi,
On the wonky pc, Look at the PORT assignment under Printer Properties and see if it matches what you think it should be.
Also, when I added my little print server (not the one you have, but probably similiar in function), the port configuration got set to RAW and my gizmo needed an LPR data-stream for it to see the printer properly, so I had to change the setting from RAW to LPR and then give it some Que name, which I used iP4500...and it began to connect immediately.