Husqvarna yth 150 tractor won't start. has to be something simple?

husq yth 150. always ran great. was mowing last week, grass a little long (not too bad though) and wet. started mowing and stopped 2-3 times - no problem. then the last time it just wouldn't turn over - no engagement of starter at all. lights worked, could hear the hour meter tick but nothing. here's what i've tried. had the starter tested, it's fine. although when i got to it it was still engaged w the flywheel, but not stuck. battery is good,put in a new solenoid, put in a new ignition switch, tested the safety switch under the seat, nothing though. are there any other safety switches/fuses? the mower gave me no warning signs. my wife was last to drive, she may have shut off mower w blades engaged. is there a relay or something w the PTO? help!!! i am back to push mowing and the leaves are turning!