My Macbook Pro crashed earlier, completely randomly. I was only running Firefox and iTunes and now whenever I try to boot into Mac OS I get a blank screen with a Stop sign icon in the center of the screen. If I try to use the install CD (holding C on boot) I just get a blank screen. If I try to enter the boot manager (holding option on boot) and then boot from the CD there, it just freezes. Really not sure what to try here, I'd really appreciate any help.