Unhandled Exception

When i start a game on lan or single player when the loading screen opens it displays the map name but below it says [no text]. and comes up with a Unhandled Exception error. scrolling down in the error information it comes up with:

info: Sim::Create() crashed: attempt to get as string a nil value
      stack traceback:

My and my friend were playing demigod perfectly fine yesterday and the error has only started today. We can do single player tournament, just not skirmish we tried changeing maps etc.