ok, try with this file. The zip contains the prepatched kext for 3850.

at boot press f8 and type -s you will see the cmd prompt, now type

mount -uw / (enter)
rm -r /system/library/extensions/natit.kext (enter)
rm -r /system/library/extensions/Atiradeonx2000.kext (enter)
reboot

download Kexthelper
extract in your desktop the previous file (3850 kext) open kexthelper and drag&drop the kext to install type your password install and reboot.

kexthelper web , look there web