I have this problem too. My Asus x550vc have Intel HD 4000 and nVidia GF 720m, so I must install 10.9 without any graphics kexts. When I was install Mac, I was install AppleIntelCapriFB kext and add flag like IntelCapriFB=9, but no vaule (1-11) isn't correct. Please help!
Sorry for my bad english.