Go into your update folder, something like this:
/home/yourloginwhatever/.local/share/mana/updates/updates.themanaworld.org
and move this folder into trash: ascii.zip
Close your client, if it is open.
When you open client, after you connect, be quick and cancel the update process by clicking the little box.
Then you see inside buildings and caves back to normal, unfettered by the dark magic of some trickster.
Edit: Got idea from "helper" in game.
thanks