Sabertooth X79 Sierra installation stuck / usb disabled

Hello this is my first attempt in to building a hackintosh and I have one issue:

after selecting Boot Mac OS X from USB the installation freezes.

tried some X79 build suggested boot flags with no luck.

one thing is odd, the usb ports all get disabled at the same point the installation freezes.

any suggestions how to troubleshoot it?

Thanks,
M.