Boot fails after 10.6.8 upgrade

ASUS P8P67LE mobo, i&2600k CPU, ATI 6870 video card.
Using two different boot CDs with their patch to avoid kernel panic.
I can install the retail Snow Leopard OS. Every time I upgrade to 10.6.8 update combo the system will boot to the desktop background but no usable OS.
Any clue why this is happening or how to get 10.6.8 to boot properly?

I have the exact same problem. Lenovo G560, used ModCD to install 10.6.3 with no problems, but after updating to 10.6.8 got stuck in the grey Apple boot screen. Am a newbie, first time trying to set up a Hackintosh, please help!