Here's the problem: our DM has talked to him a number of times. Each time has had to deal with some random issue, such as "Fred" complaining about treasure or whatnot. After such a talk, Fred chills out for a few weeks, and then starts again.
Really? I don't know you, "Fred" or anyone else in your group, but from what you've been describing he doesn't sound like he has been a friend to you at all. If he is really a friend, then he should prove it to you and the others by being respectful and putting your feelings above his. That's how real friends behave toward one another.The problem is that Fred is a friend.
Extremely unfortunate - IMO, you should be doing the exact opposite.I try my best to ignore him when he is like this (which is often), but it is getting worse. He is ruining the fun of everyone else, to a lesser or greater degree.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.