Genesis started out as a bunch of musicians, and when Peter Gabriel started developing a rather prominent stage persona, the other band members really didn’t like it. By the time they recorded Lamb Lies Down on Broadway, Peter was on one room writing the lyrics while the other band members were in a completely different room writing the music. To this day, Tony Banks has nothing good to say about that album (apart from his own keyboard solos of course). Phil Collins and Peter Gabriel somehow managed to end up friends after all was said and done.
Styx was torn apart by Dennis DeYoung trying to take the band in one direction (Mr. Roboto, basically) and Tommy Shaw trying to keep it more hard rock and guitar based. Dennis and Tommy had a very public feud going on for years after Styx broke up. They kinda sorta buried the hatchet later, only to end up each going their separate ways again.
As was already mentioned, Paul McCartney and John Lennon used to get pissed off at each other quite a bit, especially towards the end. Each accused the other of ruining their songs. Ironically, their tension and different styles ended up combining to create really good music. That didn’t stop them both from being pissed off though.
Eddie and Alex Van Halen seem to have a lot of trouble getting along with people. Eddie in particular used to get really pissed off at David Lee Roth’s constant goofing around, even though Diamond Dave’s stage presence was probably responsible for a lot of their popularity. Eddie also got pissed off at Michael Anthony to the point where even though Michael got credit on the last album he supposedly played with the band, Eddie was so pissed at him that Eddie recorded the bass parts and didn’t let Michael anywhere near the project.
The Police, or at least Sting and Stuart Copeland, do not get along well together when they are (were) working. I think Stuart Copeland was quoted after the breakup as saying something along the lines that they discovered that they could all be quite good friends as long as no one mentioned music.
Frank Black and Kim Deal of the Pixies hate each other, and only reunited for tours because of really big financial incentives. Last I heard, Kim had finally left for good and had been replaced (and the replacement was then replaced).
Kiss has already been mentioned. I saw an interview where Gene Simmons basically said they were trying to be a successful band, not friends. I also wanted to mention that Paul Stanley has had many very bad things to say about Gene’s TV show and thinks that it was not a good thing for the band at all. The last I heard the two are no longer on speaking terms because of the show.