If you see black textures: game options > interface > turn off "display world borders".
If this warning message could be written somewhere in GW, either in the faction chat window, or on the GW loading screen ("in transit" is written, I guess other messages can be written), or in the first seconds of the game when the ACU spawns, players would be able to play most of the maps normally.
It's a one time fix for a user that takes 10 seconds, and then he will never have to care about it anymore. Checking all maps that have this issue, removing them or fixing them would take more than 10 hours. Besides, the world borders really don't add much to the game's appearance.
Maybe this can be stickied, along with the GW map thread.