My printer is killing forests! Can't duplex with recycled stock

Recently, I purchased a OKI C6100 color laser printer with built-in duplexer. Unfortunately, when I use standard New Leaf recycled copier paper for duplexing (two-sided printing), the printer jams constantly. Being able to duplex and use recycled paper is extremely important to me. Are there other papers you'd recommend? Is something wrong with my printer?