My Scout was on "Auto Scout" mode... I push the End Turn button and right after that Warning message appear...
I don't have choice to push the "Yes" button cause the "No" one just make that same message always reappear. After I've click on "Yes" I've seen what was the problem. The ennemy terrain was cornered by montains and the move cursor of my Scout was right over. He was not able to move elsewhere so it's was what make the "No" not working...

DxDiag