Here's a thought:
How about manually assigning an IP address to that particular Z3100 printer? Just assign an IP other than what you may be using on the router side of things.
As well, try to setup your networking on the printer to Negotiate at a slower ethernet speed. (i.e. 10mbit full duplex versus 100mbit or auto)
I know that the auto speed negotiation setting can wreak havoc on some networks, so it might be worth a peek. Out of curiosity, what router do you have the printer plugged into?
I'm sure you've tried to swap ethernet cables as well.
Other than that, I'm running out of ideas...