I have a v. 1.0 Xbox with a Xecuter 2.1 in. Suddenly one day my xbox started this behavior with 2 x boot and then frag. I tried measuring the Lpc-points and D0 when I discovered that Lckl is 0 all the time and that D0 for a very short wile is 5 V and then becomes grounded (with no modchip). I even measured the resistance between D0 and ground when I turned on the Xbox. First it was infinety and then when powered on it became 0. So in some way the D0 connection gets grounded at power on.
My thought is that some transistor och other chip is broken (hopefully not the MCPX), does anyone know what part(s) it could be?