Christine McVie left Fleetwood Mac in 1988, and the band was forced to cancel all touring as Stevie Nicks refused to perform without her. Interestingly enough, it appears she has reconsidered. Sheryl Crow has announced that she will be collaborating with Fleetwood Mac on a number of performances as well as writing some new material with the group. While nothing is super official, Crow seems excited about the project. She hasn't toured in 4 years.