I ran into this issue twice at my work. I was charged with setting up a client's MBP, the brand new model. She didn't provide me with the grey install DVD's so I used a Leopard install DVD instead. The MBP would not boot up the Leopard DVD and let me get to the installer. Not even to the . I tried multiple DVDs, multiple versions of Leopard, and multiple methods of attempting to get it to boot up the DVD, but no dice. That same afternoon, my boss brought in Snow Leopard, and lo and behold, the MBP likes that just fine. Yummy yummy I'll install that. (good thing because I had already formatted this lady's hard drive via firewire transfer. Another futile tactic...) So I didn't think too much of this issue until a few days later when I tried to boot my own work MBP from a Leopard DVD. Mine's a model from earlier in the year, but it encounters the exact same problem! It will not boot from Leopard DVD, it gets to the grey screen, then black, then grey screen, intermittently changing colors but nothing ever happens. But again- Snow Leopard it has no problem installing. Has anybody else noticed this issue? What gives?