I have no such problems, couse I allways do something before capturing a fief... I'm sending a spy to town before besieging, and when I get 20rep I conquer it and leave the spy for some time(or U can leave him forever)...
But it won't work if U have some minus points on reputation(the spy allways end's up in the gallows...)
But it won't work if U have some minus points on reputation(the spy allways end's up in the gallows...)