MacBook Pro won't start in OS-X, but it will in Windows

Hey folks,

This is my first post as I just encountered an issue tonight - my first ever with my beloved MacBook Pro (Mid-2009 generation running Mountain Lion).

I had to shut down OS-X and go into Windows to do some work, with that completed I went back to OS-X only to find that it will not boot no matter what I try. It goes as far as the grey screen w/ the Apple logo and rotating gear and progress bar, sits there for a few minutes and then just shuts down.

I have tried:

1) Command+Option+P+R
2) Shift+Command+V

When I tried Command+Option+P+R it scrolled, as it should but it finally got to a point where it said something to the effect of "could not validate...[something]"

When I use boot camp to start Windows - no problems at all. Fires right up.

Any ideas? Logic board battery perhaps?

Thanks in advance for any input...

Reboot your machine while holding down the command and R keys as soon as you hear the boot sound. That will get you into the Recovery Partition. Once in Recovery, choose Disk Utility and verify the hard drive. It sounds like your hard drive may have problems. And yes, it's not unusual for it to be able to boot to Windows but not OS X.

Thanks, I'll try that.