TSO, wireshark trick does work. Yesterday when the FON's eth0 interface to automatically get an IP from DHCP (DHCPd gets turned on for my ethernet on my laptop once you turn on ICS) I didn't know what the DHCP range was so i turned off the FON, turned on Wireshark for the lappy's ethernet and then turned on the FON and when t he FON started looking for an IP Wireshark picked it right up.
Ofcourse reflashing the FON works too, I think i've done that 3 times :D