Why wont Redbox DVD play on my computer?

[Double]

I just rented a DVD from Redbox and it wont play or autorun on either my desktop (windows) or laptop (mac). Ive never had an issue with it before. The DVD isnt scratched and works on a Xbox 360 without any problems.
Ive gone to my computer and opened the dvd drive but it doesnt show anything. It acts like there is no dvd in the drive at all on either computer.

Any suggestions?

Update: Did live chat with Redbox and they marked the dvd for inspection when I return it and gave me promo codes for next time. Hopefully the next one will work!

[Josh]

For the mac:
Go to the program Front Row. It should give you a choice to play the DVD, and if it works, it's the most immersive DVD program you can get on a mac.

If that doesn't work, it might be because the type of code written on it is different than what is usually run on that DVD player (like PAL from the UK won't work on the DVD players in the US), and there's nothing you can do about that except bring it back to RedBox.