Hi!
I have got the same machine and burner and it works without any problems. I don't remember exactly how I installed it and I haven't got the manual here, are you sure it recommends SL (slave)? Apple recommends CS (cable select) for all drives (the other optical drive has to be set to cable select, too, and probably is by default). If it still doesn't work after you have tried that, I can open my machine and verify the setting, but I'm pretty sure it's CS.
BTW, the drive is a bit picky when it comes to supported media that can be burned with 4X speed. For me Traxdata seem to work fine, Intenso only 1X.