hi i have intel dual core e8500 ausu mbo p5q3 and nvidia gts 250 1gb,,
this helped to me, so i will post what i did. first i had also a black screen then i before boot and instalation maverics i tipe GraphicsEnabler=Yes IGPEnabler=No, after that i run instalation with no problems, and the os x recognized my graphic card. but still i couldnt boot withaout usb flash, and still i have to tipe GraphiscEnabler etc... then i run from mulitibeast bootloader chimera, and still boot from usb, after that i run easy beast option and still run from usb boot, and also tiping everytime GraphicsEnabler bla bla... and after that when i entered in osX i find folder extra and in this folder find file org.chameleon.boot.plist and in this folder i changed string where is saying GraphicsEnabler-NO to Yes and string where is IGPEnabler=yes to No. and after that i restart pc, and boot it form hd with no problem..
Sorry for writing errors but i hope that this will help you..