I upgraded a 2011 MacBook Air to Mountain Lion, however, it isn't playing nice with some enterprise things, so I want to put Lion back on it again. Booting the Air with a USB stick containing the Lion installer doesn't work (see photo below). I booted it off a USB stick containing the Mountain Lion installer instead, and loaded Disk Utility to wipe the hard drive, because I thought it would refuse to boot the USB stick containing 10.7 if it saw 10.8 was installed. Anyway, that didn't help, because I still can't it to boot from my Lion USB installer. When I hold alt and select the Lion installer, I get this screen for about 10 secs before the machine shuts down. I've re-made the Lion USB stick, and I'm using the same USB stick that I used to make the Mountain Lion installer. Any ideas?