I've been using JA for a long time and I uninstalled it. When I just recently installed it, the game worked somewhat fine. All of the files are there, but now this error message gets displayed whenever I try to join a non-default map.
I've been trying to figure out why, but I am inevitably unsuccessful. Any help would be greatly appreciated.
reinstall it again is my guess
I already have. I've tried many things. All of which, seem not to have any effect.
I would suggest you move any custom mods that you have recently installed and could possibly be affecting your game out of base, then restart your computer.