No Entry at boot

I have my Asus laptop in AHCI Mode (I think). I then load my iBoot CD which works fine. I then put the Snow Leopard 10.6.3 disk in. A grey screen with a dark grey apple appears. This has a loading circle underneath it.
After about 30 seconds a No Entry icon appears just above the Apple logo and the install goes no further.
Any ideas what might be wrong?
Thanks
P.s Sorry if this has been posted already, I did look!

After you put the SL disk in, wait 10 seconds, then press F5. Then use the arrows keys to select the Snow Leopard disk, type "-v" and you will see output of what is happening "underneath". Then you may be able to diagnose the problem better.

TonyMac's instructions for iBoot/Multibeast method give other things to try if you can't boot here.

"Still waiting for root" seems to be the problem