TomatoUSB

I am a complete noob and flashed a Linksys E1200 so that I can access US TV content while traveling in Mexico. Hooked it all up and all good so far. However, the new Cisco network is not secured and if I try adding a password I get the following message "Cannot proceed: two or more LAN bridges have conflicting IP addresses or overlapping subnets". I assume I need to change IP settings, or something. Any guidance would be very much appreciated.

Thanks!