Seat switch is defective, or the seat switch is not adjusted properly, or the seat switch is unplugged.
The reason for this is because the engine is permitted to run when the seat is empty ONLY if the brake pedal is locked down.
If there is a fault regarding the seat switch, when you try to let up on the clutch/brake pedal, the seat switch "thinks" the seat is empty......and kills the engine just like it is designed to do.

To Mownie - We had the same problems and thought the same thing. We "rigged" the seat switch so that it would permanently stay in the compressed position so it would think someone was in the seat, but we still had problems. Mower would run fine, then just die for no reason, then refuse to restart. My Husqie was nothing but a problem from Day 1, and I am currently looking to replace it, even though it only has 92 hours on it. Two friends of mine have Husquies, also, and they've had nothing but trouble with theirs, also. As far as I'm concerned, they are nothing but a piece of junk!

Too bad you feel that way about your rider. No matter what kind of equipment you use, it has to be maintained and treated w/ respect. Back to the funky safety switch question. I have had on occaision, have the tamperproof feature of the seat safety switch malfuntion. It's the liitle spring that closes the contacts of the connector on models w/ the grey switch. It's there for people who don't value their safety and others around them by disconnecting the seat switch. You can pry out the little center piece and remove the spring- then plugging back into a fuctionally set up seat switch and still have a safe rider.

To Mownie- Thank you so much. You are so right. My seat switch wasn't plugged in correctly. After I reconnected it. My husky back to work. Thanks again.

husky2448,
You are welcome & thanks for the positive feedback.
k9quad, after you find a replacement for your Husqie, please send it to me. :^)