Hey I'm having the same problem, think maybe it's not flashed right, because if there's no bios the mainboard would freak out that's what the 3 boots is I think.
But if you read my post on XBOX 1.6 then you will see all the trouble I went through to flash it.
I dunno, I'm getting very upset DMS needs to answer some questions, there's too many people asking questions and noone answering, I would like to know which direction the pin-header installation goes and would like to see how to rebuild the LPC on the 1.6. But the only 1.6 tutorial I've see from DMS is with LPC rebuild chip.
I've only got the 1.5 chip without the LPC Rebuild chip.
-Matt