Mac Pro OSX Lion "No bootable device -- insert boot disc and press any key"

On my Mac Pro OSX Lion... i have a "No bootable device -- insert boot disc and press any key" screen after successfully installing and running Windows Professional 64bit on second internal hard drive with bootcamp. Was able to boot both Windows on second drive and OSX on first drive and did so for a week. Then I decided I wanted to run that version of Windows using VMware on my Mac Mini. So I started up Mac Pro with OSX, went to disk utilities and erased / repartitioned for Mac the second drive that had Windows. Shut down Mac Pro, started up Mac Mini and successfully installed that Windows version using VMware. Restarted Mac Pro the next day and realized second drive was not usable and was mounted on desktop named "Windows" instead of the name "Mac Pro 2" I had renamed it when I erased and repartitioned. I did some online reading and opened Bootcamp Utilities to try and properly erase Windows and repartition. Couldn't get past first step in BC utilities as it didn't recognize second drive either. Sighed and shut down Mac Pro. Today started Mac Pro and got the black screen with "No bootable device -- insert boot disc and press any key". I forced shutdown and restarted holding down the alt / option key and got same black screen. i shut down it again and restarted holding the X key and got the same screen. I shut it down, opened the case, pulled out second drive, and still got same screen. Why in the world can't I boot OSX from first drive? I even tried booting from Lion backup USB and still nothing...very strange.