2nd Boot from USB - Stuck on Apple Grey Screen

[jjc777]

I'm having trouble upgrading to Yosemite from Mavericks - after installing from USB and restarting, my attempt to boot from the USB into my new install gets stuck on the Apple grey screen, with what looks like a progress bar underneath (the progress bar does not move).

I have an old Sandy Bridge-based system with Award Bios - Gigabyte GA-Z68MA-D2H-B3 motherboard, with i5 2500 CPU and GTX 660ti video card. I used the legacy support when I created the USB installer with UniBeast due to the Award Bios.

I have tried a few boot flags based on information I've found around the site: PCIRootUID=1 and PCIRoot=1 (separately and together) resulted in the same issue. Using the -x flag to boot into safe mode gave me a "Can't find mach kernel" error.

Any advice?

 

[thearod]

Doing my first Yosemite install from Mountain Lion today thinking that all the bugs had been worked out. But I am getting the same exact thing. After running multibeast 7.3 and trying to bring the system back up it hangs at the grey apple loading screen.

I tried -x GraphicsEnabler=No PCIRootUID=0 to no avail. Something weird happens after I try to load it twice, I get no video on POST. I tried everything to bring it back and the only thing that seems to help is unplugging it and letting it sit for a while.

 

[Asus-Freak]

That's because there is no mach_kernel in Yosemite. Of course if you did a search here for "Can't find mach kernel" you'd already have the answer. Search is your friend...

 

[usong]

My system is different than yours--see my profile--but I was experiencing the exact issue you are having after the 2nd boot from USB. Well, this problem disappeared as soon as I reflashed my MB with the latest BIO from Gigabyte. You might give that a try.