This same exact thing happened to me, except I had only completed around 40 missions. I tried everything, and spent over a week of in-game time driving around and doing side-missions, before I came to the unfortunate conclusion that this is just one of those uncommon glitches in the game.
I hate to tell you this, but I think your only solution is to load an earlier save, if you have one, or start a new game. That's the only thing that worked for me.
Oh, and I'm new to this site--well, I've been lurking for a while, but I just registered today--so hello everyone.
