hi, i installed snow leopard on 3 different ways now and everytime i get the same result: after restarting my screen is black and my keyboard turn off. so any ideas how to fix this problem? do i need any special kext for my mainboard?

amd x2 4850e
foxconn a7gm-s (amd 780g / sb700)
corsair xms2 2*2gb ddr2 800
foxconn 8800 gt (g92) 512 mb

greetz rora