statesman clutch issue?

have a 20 hp/50in cut statesman circa 2000, today without warning, the clutch/brake decided to disengage, thereby not allowing mower to move unless i put my foot under the clutch and pulled up so it would release the brake and engage the clutch. i am sure it is just\ an adjustment but i just acquired this mower a month ago and this occurred during the third cut...i can get it to work but not comfortable holding brake up with foot..sort of dangerous but i got the yard done...any ideas on this