Plutonium

When I launch zombies, it works fine, but I start multiplayer and the bootstrapper starts to load, but it crashes and I am met with the error message 'Couldn't load image "menu_mp_map_select_area51". I checked the bootstrapper and the final line before the error message says 'iwi is missing'. The game and the launcher are up to date. Any known fixes for this?

Whenever I try to play private zombies with my friend, we can't get it to work. He opens the plutonium menu(F10) within the game, double clicks my name and nothing happens. The same occurs when he types in the "connect" command with my IP and the dedicated port, and the console just closes without any response. If I host a private match and I type in my own IP with the port, I can join my own game. Both of us enabled Plutonium through the firewall, I also forwarded a port and the game says UPnP is enabled for me, but for him it isn't. What is really frustrating is that I don't know if the problem is with the launcher or our routers aren't compatible in some way. Any help would be much appreciated.