Hmmmm, 266 -> 270 shoudn't cause any problems....ugh, try reducing the multi to 7x, bump vcore to 1.475V, vmch to 1.7, vfsb to something in the middle, RAM to '533' 5-5-5-15 2.3V, and set 401FSB. See if that does anything....if not, try all that, but with FSB settings at 301/335/368.

If none of that still works, ask your contact if they know what's up.