[Sombre]

You both need to have the mods and probably have to have enabled them in the preferences as normal. Other than that, I don't know what to tell you. I know it is the mod files on the server's install that are actually used, but everyone needs to have the .dm file and graphics and whatnot - if the client has a slightly different version it can cause problems, since they'll see things differently from the 'actual' copy used by the server.