Hi,
I have an ASUS H61M MB w/ 803 BIOS. Ubuntu works fine, Debian 7.8 worked fine but when I installed 8.1 the BIOS disables the drive (on boot) w/ 4.xxx or 5.xxx depending on the number of partitions. I switched which drives debian and ubuntu were on and the disabling moved to the drive debian was on. The safe boot is set to other OS. good-bye debian