Show_err barely works for campaign bugs.

The problem is very likely that you moved the general out, but he is now in a rebel province or he is located on an invalid tile. Check the coordinates of where he is standing and look through map_regions.tga, map_ground_types.tga (check for mountains or dense forests as they are the two that cause problems) and map_features.tga. Remember to double the size of the coordinates for map_ground_types. Move him onto a tile that you know is valid and you know is within one of Britannia's starting provinces.