Assuming you have the proper subnet mask and gateway info, I had a similar issue with a Phaser 7800 after a firmware upgrade. I'm not sure why, but the interface only started working after 2 shutdowns of the printer. The first was a shutdown and unplugging the printer power, no luck. Then I switched from DHCP to static IP (the DHCP provided address was working previously). Did a shutdown and power up again and it worked!
Trying to troubleshoot network connectivity isue with the printer. I am able to see the MAC address of the printer so I the connectivity between the switch and printer is working but when I try to ping or start the web interface I am not getting a response.