Agree with all the guys, but above and beyond the blade being on backwards, it has to be the speed and feed that is causing the problems. I would check out the BLOGS at www.bandsawblog.com I'd bet you're just bouncing the blade across the material!
They write informative blogs often during the week which I have found to be very educational and informative. They are attached to www.sawblade.com who have the best prices on American made HaltbarSagen engineered band saw blades.