I agree with Saint Ehlers. I know that doesn't offer much help to you 42, but sometimes we have to palce the blame where it is due. If you have players that are immature and/or meta-game thinkers, there is not much you as a DM/GM/Storyteller can do to cater your story to them. I have been dealing with a player like this for years, and it has been very difficult as the rest of the players have evolved into wanting a greater role-playing aspect to the game, and he just wants to be the best at everything. The way the other players and I have dealt with the situtation is to have him play a character type that is a "jack-of-all-trades," find out what sort of mood he is in with this character (fighter, mage, rogue, etc.) then try to evolve the character along those lines. This may not work with your particular situtation, but it has been fairly successfull for us.
Most importantly, "the needs of the many out-weigh the needs of the few, or the one," and you as the DM/GM/Storyteller, eventually have to play the role of "God of your universe" and nudge the character down a path, or away from a path, accordingly. I tyr to do this in game as well as I can, but sometimes it doesn't always work out that way. Don't sacrifice the enjoyment of everyone else for just this person. If they get bored or frustrated, tough. Life, whether real or role-played, aint always the way we would like it to be.