You did have to do MAJOR, MINOR on Medieval.
1) Go into the Medieval II - Total War folder
2) Go into 'data'
3) Go into 'World'
4) Go into 'Maps'
5) Go into 'Campaign'
6) Go into 'imperial_campaign'
7) Right-click on 'descr_strat', go to properties, and untick the 'read-only' box. Click 'ok'...