re: problem with macbook pro retina on startup. help

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ETA: I do think you're right though. That looks like a windows boot error message and the OP never answered if he has WIndows install on there, did he?

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It's not actually a Windows boot error message either. Macs use EFI firmware, and when there's no EFI-bootable volume they come up with the flashing question mark folder like you mentioned earlier. But the EFI firmware also includes a BIOS-boot compatibility option, which is used to boot non-EFI versions of Windows (pre-Win8). When you attempt to use this option and the partition isn't there or is damaged, only then will you receive the error the OP is getting, and it's basically the firmware telling you that Windows is missing. This usually only really happens when you set your system to boot to Windows by default and then delete the Windows partition.

The mystery to me though is how he would get that error message when selecting the Mac partition. That makes no sense to me.