if your fragging the xbox is having trouble finding the bios, here are some possible solutions
did you have a working bios on both banks of the chip? maybe you accidently swithced the bank the chip is loading from
you didn't mention flashing your chip, but if you did bad flash/incompatible bios?
if still no go, check your lpc connections, if the d0 is grounded but a wire popped off or your pin header isn't making good contact, the system won't be able to find the bios on the lpc bus.
lastly look for solder spills, lifted traces etc.
when you say xecuter 2 toggle switch, i'm assuming you mean the 2.0 since all newer versions comes with the switches. try pulling off the on/off jumper on the c hip to see if it will boot to the ms dash like that (or if your xboxdash.xbe isn't the msdash go to a "your xbox needs servicing screen" with the error code corresponding to unable to load the dashboard) instead of fragging.