All,
Being a N/W developer, usually I face this problem. There is very simple solution for this.
1> Connect that device with a "Cross-over" N/W cable to another computer.
2> Start a N/W packet capture utility (tcpdump/ethereal/snoop) on that computer
3> Restart device
4> When device start it sends ARP broadcast containing its own IP-Address. This is done to ensure that no other device is assigned same IP.

5> After getting that packet with IP-Address (Example 192.168.2.13) you can assign your computer a smallest possible subnet mask (255.255.255.252) with another IP in that "smallest" Network (Example 192.168.2.14/255.255.255.252)
6> Now access that device with any of login/configuration service

All the Best!!!