I have a Macbook Air 11 Ultimate and I was having issues with 10.6.7 (playing Portal/Netflix) hoping that downgrading to 10.6.6 will help. So I want to reinstall SL and get back to 10.6.6, but trying to do a reinstall with my SL dvd is not working. I get to boot off the DVD with the option key, and it allows me to select the dvd to install, but right after that I get a box saying I have to reboot (in multiple languages). I get this same result from a SL USB drive or a SL DVD. I lost my USB thumb drive that came with the macbook. Any suggestions?