OS X Leopard Install Woes

I'd like to have woes installing Leopard, but I can't even get the install DVD to mount on my MacBook Pro.

It takes the disc in, then 5-10 seconds later it spits it back out. It also does this for a Modest Mouse DVD I happened to have lying around.

Ah - it's a mechanical problem, then.

But noooo. It can mount

• the OS X 10.4 install DVD.
• the recovery DVD from my wife's Emachine.
• the Wii-Fit DVD. [1]
  

What the hey?

[1] Which, by the way, is about a slick bit of software and hardware.