Same here...
I can click on 'confirm' but i can't leave that screen. Clicking 'save' produces that same error. Hitting enter after entering a callsign does the same. If i try to move elsewhere in menus i getError
user already have a profile for battletech
After alt+tab & restarting BT i got to the main menu though. And it seems i can start the campaign regardless of that errorError
Please enter a Callsign