i have found some tips :
solution1:
Perform NVRAM reset in service tools before machine reboots again. caused bu corrupt nvram (makes sense maybe because you did a firmware upgrade) http://www.support.xerox.com/support/7760/support/en_US.html?objGUID=3965
solution2:
The Configuration Card stores the network settings. Sometimes the values stored in this card can cause the printer to re-boot or hang. To help make the printer more stable, disconnect the printer from the network and make a few changes to the printer's network settings. The recommended changes include setting the the printer to a static networking speed and turning off any unused networking protocols. On the printer's front panel, set a static networking speed, rather than leaving it set to Auto select. 1) Press the [Up] or [Down] arrow button until 'Printer Setup' is selected, then press the [OK] button. 2) Press the [Up] or [Down] arrow button until 'Connection Setup' is selected, then press the [OK] button. 3) Press the [Up] or [Down] arrow button until 'Network Setup' is selected, then press the [OK] button. 4) Press the [Up] or [Down] arrow button until 'Ethernet Speed' is selected, then press the [OK] button. 5) Press the [Up] or [Down] arrow button until the desired networking speed is selected, then press the [OK] button. NOTE: If there is no networking administrator to find out the network's speed and type, look on a configuration page if one is available. The network speed and type can be found under the heading PhaserShare Series B Interface for Ethernet Network. If no configuration page is available, try the most common setting: 100 mb / Full Duplex. Turn off any unused networking protocols, especially: SLP, SSDP, and EtherTalk if there are no Macintosh computers on the network. To turn off SLP or SSDP: 1) Press the [Up] or [Down] arrow button until 'Printer Setup' is selected, then press the [OK] button. 2) Press the [Up] or [Down] arrow button until 'Connection Setup' is selected, then press the [OK] button. 3) Press the [Up] or [Down] arrow button until 'Network Setup' is selected, then press the [OK] button. 4) Press the [Up] or [Down] arrow button until 'TCP/IP Setup' is selected, then press the [OK] button. 5) Press the [Up] or [Down] arrow button until 'SLP' or 'SSDP' is selected, then press the [OK] button to toggle it from On to OFF. 6) Press the [Up] or [Down] arrow button to make another selection in the menu, or press the [Back] button to exit that menu and return to the previous menu. To turn off EtherTalk: 1) Press the [Up] or [Down] arrow button until 'Printer Setup' is selected, then press the [OK] button. 2) Press the [Up] or [Down] arrow button until 'Connection Setup' is selected, then press the [OK] button. 3) Press the [Up] or [Down] arrow button until 'Network Setup' is selected, then press the [OK] button. 4) Press the [Up] or [Down] arrow button until 'EtherTalk' is selected, then press the [OK] button to toggle it from On to OFF. 6) Press the [Up] or [Down] arrow button to make another selection in the menu, or press the [Back] button to exit that menu and return to the previous menu. Turn the printer off and plug it back into the network. Turn it back on to see if the re-boot or hanging problem is resolved. If the above did not resolve the problem, or if you're not able to get to the front panel menus, replace the Configuration Chip. This part is easily accessed by removing two phillips screws at rear of Image Processor board and sliding board out the rear of the machine. The chip installs on the top of the board. Then follow the above network setting recommendations BEFORE plugging it back into the network.
