I'm having the same problem. DVD player isn't playing commercial discs that played perfectly in the past.
The previous links mentioned don't seem at all related. My drive is an internal one and they say not to remove the battery for an SMC on this model of MacBook.
I thought it might be the computer's entire drive was busted, but I can burn a DVD just fine it just won't play it. So I'm wondering if it's the DVD player app. Is there a way to re-install the DVD player app? Is this a 'Genius Bar' fix?
Thanks for continuing to work on this issue.
Mine: MacBook Pro, OS X Mavericks (10.9.4)