In this situation, either you or the Host don't yet have the latest Run8 Update installed, and therefor it's a problem of two different versions of the sim trying to connect.

The Host and Client must both be using the same version of the sim, otherwise certain network functions are incompatible. Basically, they can't talk to each other properly.

The latest Run8 version update can be found on our website at http://www.run8studios.com/updates_dlc.shtml