Here's my problem: I've downloaded a copy of OSX Mountain Lion from the App Store on my MBA and created a USB Installer. I've upgraded the SSD on my rMBP. It currently has one with no OS on it. When I try to boot up w/ the USB installer to install Mac OSX on the rMBP, instead of going to the Apple symbol, it displays a circle w/ a line through it. I'm able to boot into the USB installer just fine on my MBA. Is the reason for this because I need to download Mountain Lion OSX from the rMBP, so that the right drivers, etc.. for the rMBP are also downloaded with that installation? Any insight would be appreciated.