have you removed the video card and tried booting with just onboard video.) bios 0701 fixes hang with 680 cards.
1.Improve Improve system stability.
2.Enhance compatibility with some USB devices.
3. Fixed Nvidia GTX 680 hang when runing with UEFI driver.
4.Support new CPUs. Please refer to our website at: http://support.asus.com/cpusupport/cpusupport.aspx?SLanguage=en-us