I've finally booted into Mavericks flawlessly.But I wasn't using Niresh's Maverick, Unibeast instead, as I tot it was the USB Installer's problem.Just sharing what I did as I think it might worth a try.I guessed the problem is caused by the HDD MBR partition together with the Windows 7 running on the same hdd. So I downloaded and replaced the modified OSInstall.mpkg and OSInstall framework from here: http://www.macbreaker.com/2012/08/mountain-lion-mbr-unibeast.html In Bios, disabled intel vt-d (Intel Virtualization Tech). Repartitioned my hdd, but still MBR as I've already replaced with the modified version. Then boot installation USB and Mavericks HDD with -x, signed in to Mavericks, ran multibeast and OS booted successfully after that. =)ï»¿My PC: DELL XPS 8500 i7 2600, 8GB Ram, Nvidia GT640, Seagate 2TB.