I think renown has a lot to do with whether a fief is offered to you or not. In my .890 game (which, tragically; is now incompatible) I amassed 2590 renown and the King offered me every Castle fief I conquered without fail. But now, I've conquered several Castles and I've only been offered one of them (Vincoud, renown of 100).
Also, Meltor had the nerve to rest at Vincoud without even asking my permission. I was there to collect taxes, and suddenly spotted "Meltor's Party" under the title.
"What the hell ...?" quoth I, stealing into the Lord's hall. Sure enough, there stood Meltor, with his cape and everything. When addressed, he said "Do I know you?"
"Well, yeah; I own the damn joint!" exploded I.
"What do you want?"
"To crack open your head, and paint my fief with your brains!"
But, of course, you can't kill noblemen ... just yet.