I haven't installed Win8 so I do not know if boot process is the same as previous versions of M$
Have you tried https://wiki.sabayon.org/index.php?titl ... tore_Grub2
or reinstall grub using install to harddrive from livedvd
Desktop ASUS M2N-MX SE Plus, AMD 64 X2 Dual Core 5200, 4 Gb RAM, GeForce 9500 1GB
Notebook HP CQ61-311AX, AMD CPU M320, 4 Gb RAM, Radeon HD 4300 512 MB
Wireless AR9285, Audio ATI SBx00 (IDT 92hd75B2x5)
Some mistakes are too much fun to only make once!