Which maps are you trying to play?

The ones im trying to play are SOG, Kino der toten, and Titan Corp UGX. Buts its only when I try to play co-op. And I dont want this to happen if I try to play other m...

If its happening with downloaded maps check

C:/Users/AppData/Local/Activision/CoDWaW/mods/

Look in the mods folder for any files that aren't in a folder.

I did, no loose files...

I keep getting this error on some maps but not every map when I try to play with a friend. When I play solo it works fine. Its only when we try to play coop. How do I fix this?