Dura -Force Self Propel Not working

Oh boy . If this is not a classic. So my Neighbor from across the street comes over ,and asks to use my Lawnboy ,says he was almost done with his yard ,and his Lawnmower conked out ,and he had like 4 strips left to cut. The thing is ,the day before ,he had helped me hang a piece of sheet-rock in my garage (5/8) ,so heavy ,on the ceiling ,where I had water damage from a leak ,so I felt ,I couldn't say no . Well he returned it 10 mins later . and I thought nothing .But the next day ,I fired it up ,to make sure it still ran ,and it did . Well the next saturday I went too cut my lawn ,and it was not responding to the self propel cable. I checked ,and the belt was not broken ,it seems to disengage ,but no pull at all. Is the Clutch fried or something? Any help appreciated! Thanx.