Prog-rock kings Yes have been forced to cancel their entire 40th anniversary summer tour because vocalist Jon Anderson has health problems. Last month, Anderson was taken to the hospital with an asthma attack. Doctors then diagnosed the vocalist with acute respiratory failure and recommended he rest for at least six months. "In the wake of my recent respiratory attack, doctors have advised me to spend the coming months resting and recovering," Anderson said. "I'd like everyone know how deeply disappointed I am by this turn of events." No rescheduled dates have been announced. Also, the live album documenting the tour has obviously been scrapped.