It happened to me once... tried everything in my arsenal but couldn't fix it... as you did the only way to solve it was to re install everything, losing careers and all the info....
Sorry it happened to you too ... however, then I learned to make a backup of my careers so if it happens again, I can restore them to the "Documents" folder after reinstalling SH3, no matter what version you use (GWX, GWR, Onealex, CCOM, LSH3, whatever)...