I have similar problems.......
eg: ver 1.1 with header pin & x2.0 lite installed with D0 grounded
boot x2.0 up - remove x2.0 / hotswap - plug on duox-2 and flash with say 4981
yup that went fine and turned itself off - booted back up on the 4981 and flipped switch to other side to put on a bios with embedded eeprom so it was gonna become a versitile mod for most xbox's (no 1.6's coz 4981 ain't compatible I know but this was gonna be for the older xbox's was my intention)
anyway flashed it with embedded bios and turns itself off
goes to power xbox on - 3 resets on either bank - wtf ?
remove duox-2 - boot with x2.0 or a cheapmod - all fine
turn off xbox - swap mod back to duox-2 and it boots ?
power off - power back on - 3 resets - WTF IS THIS SHIT

Now this is the second time I noticed this - the first duox-2 was when I was gonna use it on another xbox - thought it was 1.2 but was missing LFrame so x2.0 or cheapmod no good for a 1.3 xbox
with the 1.3 it was frag/3 reset stuff when the D0 was premanently grounded as in a cheap lpc mod install - oh sod this so had to crack another xbox open to pull out a duo-x 1 mod that did work no problem
WWWWWWWWhhhhhhhhhhhhhhhoooooooooooaaaaaaaaaaaaaaaa
soz for long post but giving detailed examples before anyone says ah but did you do this n that - I'm not a complete noob
Both the 1.1 & the 1.3 work fine with the header pin all installed etc.... but note the D0 is permanently grounded:
Duox 1.0 - no problems with a D0 - Ground connection
2 x Duox-2's seem erratic if there is a D0 permanently grounded
Both these Duo-2's work flawless in 1.6's with the BT & D0 wired onto mod
Being that they changed something on the Duo's when they made the duo-x 2 - in other words the duo-x 1.0 don't work properly on 1.6's with it's smart/switch enable - found that out to be true
So if they changed something in the switch/enable circuit's the way D0 is grounded or the way it pulses so to speak - is that why if you try n use it in an older xbox with D0 - Ground always on you sometimes get problems ?
Chancer - when you have installed them Duo-x 2's in older mobo's was that with BT & D0 wires into the mod ?
Anyone else tried or had problems wiring the D0 - Ground with Duo-x 2's and had strange results problems
coz this is freaky if you want a quick mod that is always enabled
if so - bloomin' shame coz I think they are excellent mods