Network Printer, the bane of my existance

So I have some printers I need to get plugged into put onto the network. I have Server 2008 set up with Print and Document Services. The printer is an HP Laserjet p4515tn. So here's what happens:

I configure the IP, Subnet, DNS, etc etc on the printer through the printer keypad. BUT, when I plug in the printer to the network, the keypad locks up and I have no control over the printer. When I ping, it's real sluggish, often at 4 or 5ms response time and I often get 1 or 2 "Request timed out."
BUT heres the fun part. IF I plug it into a network switch with nothing else plugged in, the keypad responds just fine.

This is really beginning to irritate me. I know the USB works and so I'm considering just investing money into some print servers, but I'd rather not if I don't have to.

Thanks for the help.

You may have a bad nic or firmware in the printer. Have you contact HP. I always have trouble with HP drivers. Whether it is usb or network.

HP support and I don't get along. Haha.
I'm attempting to update the firmware right now. If that doesn't work then I guess I'll suck it up and call HP.