After some issues this weekend, I've was forced to troubleshoot a Mac. However, with Apples proprietary hardware and without the POST information from a PC it can prove rather difficult.
So after a little late night Googling, this is what I found, a great little utility called AppleJack.
AppleJack is a user friendly troubleshooting assistant for Mac OS X. With AppleJack you can troubleshoot a computer even if you can't load the GUI, or don't have a startup CD handy. AppleJack runs in Single User Mode and is menu-based for ease of use.
And my does this work! After installing you can after a restart Command - S and simply type applejack when you hit the command line to reach the diagnostics menu. Just a few seconds to install is all you need and this may just save your bacon! Follow the link below for the install guide and the AppleJack project page.AppleJack Project