When you have more then one interface with a route to a client, it send the information over the default interface/rroute, (not the from where he got it the package) don't know if this is fixable, but could preven connection issues in some caes .... (when you have more then 1 internet connection)

I'm not quite sure if this works or not, but try launching nexuiz with -ip ip_of_the_interface_you_want_bound

I know it works for servers, I'm not so sure about clients however.