I agree completely with the analysis by CrystalBlue, but I offer another solution.
A group of people playing pen and paper is usually a group of friends, or at least people that are somewhat friendly with each other. There are some things only a DM can do, such as preparing a campaign. But the DM is not the boss of the group. For example, anyone can invite the others over to their house for a pizza and a roleplaying session as long as the DM is somewhat prepared.
What I'm saying is, some things are the responsibility of the group, not the DM. A single player that doesn't really play along because of unknown reasons is one of these. Someone needs to talk to that player. Since the player's problem doesn't seem to be the campaign, that someone doesn't have to be the DM. You can ask someone else to talk to the player one on one, which may be the wiser choice depending on the group dynamics and how you all know each other.
And even if the problem is how the campaign is run, using another player as intermediary might help. Maybe that other player then tells you that the problematic player does have a point and there are indeed things that you should do better.
