True, but until the next patch appears it 'solves' the issue.Would work, but that file will get overwritten by updates, which is the bad thing about editing any of the actual game files.
That did the trick, The Loot, thanks. Disabled Tech Diffusion, loaded my savegame, selected GP and the game plays on normaly.
Are you able to save after you choose your great person, reload the disabled Mod and continue on normally?