What is the movie where husband some writer or editor and wife works with a rock band cheats on her husband?

You're likely thinking of the movie "Almost Famous" (2000).

Here's why:

* The husband: William Miller, a young aspiring journalist writing for Rolling Stone magazine.

* The wife: Penny Lane, a groupie and the girlfriend of the band's lead singer.

* The cheating: While not explicitly shown, the implication is strong that Penny Lane has an affair with Russell Hammond, the band's lead singer.

Let me know if you have any other movie details in mind!