Wow, I am having the same issue with C3765dcn MFP's. I have flashed the firmware, swapped boards, memory and it still does the same thing. I even changed out the switch it was connected to updating it to a much newer and better Cisco layer 3 switch. I have changed the patch cables etc. Nothing seems to fix it. Dell was on site and replaced the board but it did not fix the problem. Very strange. Hope this helps incase someone figures out what is going on.
Please post here we keep having to reboot printers on segments we scan. Seems to only effect Dell Printers. -WS