Break-Up: Believe it or not, tension surrounding the soundtrack to Twister caused Sammy Hagar to leave Van Halen in 1995. The group had just finished a long world tour, and a worn out Hagar was unwilling to fly right back to the studio and continue work on a song for the disaster movie. When all was said and done, Hagar left the band.
Reunion: An ill-fated LP and tour with Gary Cherone convinced the Van Halen brothers that they needed their old singer back. Both sides had talked a lot of shit over the years, but they put that aside to record some new songs for a compilation and launch a tour in 2004.
Duration: A little under a year. The tour coincided with the peak of Eddie Van Halen's alcoholism. Hagar and Eddie had horrific clashes on tour (detailed in Sammy Hagar's amazing autobiography) and neither party has spoken with each otter since the final show in November of 2004. That's also the last time Eddie spoke with original bassist Michael Anthony.