I have an 8 week old mac pro running 10.8.2. Two 2TB internal drives... main and Time Machine. Everything has been running smoothly, until yesterday. When I boot the machine, it starts as though it was a new system install. The first screen to appear is the one asking what language I want to use, followed by "fresh install of OSX" or "restore from time machine" or "open disk utility"... you get it. Why would my machine act like this out of the blue? The only way to boot from the main drive is to hold down the OPT key during boot and select the primary system drive. Once it boots, everything works as it should. Help... and thanks.