I dont get it....

The very first xbox i done i had no problems out of what so ever, the next 2 i obtained will not boot one goes to error screen with an error 6 i think and now the newest one i got boots to the error screen and doesnt even show a code in the corner, i used xbhdm1.9 used the right eeproms and all and both of them boot up with a flashing green/red led. i dont get whats going on here ive checked the drives and they are lockable and are working fine according to other users posts, these are all softmodded boxed using knaves endure dual boot open=retail, i just cant imagine why the first one worked just fine and was so simple i thought i could mod them all, but these 2 are complete pains in the rear and i dont want to try and unlock the original drives because i dont want to lose what little functionality they have with the original drives, i dont want to unlock the original and then relock it only to come up to another error screen please i beg for help of any sort because i have a good bit of money tied up in these 2 boxes and i cant get them to work, any help would be greatly appreciated.