My mac boots to a grey screen - target disk mode works My macbook boots to a grey screen - BUT the hard drive is OK.

I tested it in target disk mode and the drive loads fine on  my other machine, so I can only assume it is something to do with the display.

I've reset the PRAM/NVRAM , can anyone offer any advice on how to proceed from here?
Boot to Single User Mode (Cmd S) let it do it's thing and then type: 
cd /var/log
(press enter)
grep disk0 * 
(press enter). 

Towards the end of the outputted logs if you se IO Error your hard drive or flex cable are going. 

If you can boot in safe mode (holding down shift at start up) maybe you have a dodgy 3rd party kernel extension.