Has anyone noticed this? If you start installing Lion (also applies to Snow Leopard or Leopard) from bootable disc (USB or optical), without AC plugged in, during the first half of the installer, if the screen goes black (dims), and this preveals over reboot, there is no way to get the Mac "reponsive" again, even if the battery is fully charged. The symtoms are .... no sleep indicator Led ... black screen.... trackpad button and keyboard is un-responsive (not sure about backlight) The only way you can tell that its still operational is by the sound of the hard drive. The above permits even after install, when you first boot to Welcome Screen if left. So you must power off and back on to resolve.. I've been though about 3 MBP's, all having this same issue. I'm just wondering weather Apple has fixed this with Ivy Bridge. As its clearly a Mac issue.