OK, if what I read above is correct you are noting an article that talks about being able to get a 2.6 to use the first 256K of the X3 bios. It is NOT reversible, you CANNOT use the X2.6 Bios in an X3. If you flash a 256K Bios to a 1MB bank it will cause an error since at the 257K mark it will be empty and the chip is still looking for instruction.
You CANNOT use the 2.6 Bios on an X3, it's stated all over this board.
WHY THE HELL would you continue to want the X2.6 Bios on your X3??
Was your X3 not functioning properly and you decided that a 2.6 Bios might work?
We CANNOT help you if you don't help us understand what's going on.
To get back to FlashBios, even in the backup here's the suggestion.
move the switch to a different bank and then use the backup button combo.
(Power slightly before eject, then hold them both.)
I don't know why, but having the switches set to a different bank to use the backup bios works.
BTW, if you hold power for even a second when you turn on the xbox it will disable the mod. To get the mod enabled (blue light) you pretty much have to do a lightning strike on the power button (QUICK!)
(Only excepting when you are getting to the backup bios)
You can also enable the mod easily by using eject to turn the box on.