You will commonly see the abbreviation KTM used in the modding forums it means Kick-back To Menu.
It refers to type of 'crash' when you attempt to load a campaign or custom battle but instead of seeing next loading screen you get returned to a previous menu.
Most KTM's give an error message if you are using the -show_err system in RTW/BI. For this sort of problem you do not see the error message until you attempt to quit the last exit screen in the game.
For M2TW you will not get an error message when you quit program, instead you need to refer to the log file.