[Kos-Mos]

Well, the AC is basically a laptop PSU built into the charger.

I have a B6 non-AC, and I had this error when my old 10A PSU was dying.
Replaced with a modified PC PSU that can supply plenty and it works fine now.

The error basically says that the voltage dropped under 11.0v.
Most of the time, if the PSU can't supply enough current, the voltage will drop to compensate and screw things up.

Sucks, but that probably means that you will need an external PSU for now-on.

If you want to use a PC PSU to test, you just have to put a metal paper clip between the green and a black wire in the motherboard/24P connector. That will start it up.
Yellow is +12v, black is 0v/ground.

If you want to use the PSU long-term, you need to modify it a bit otherwise it will blow.
10ohm, 10W ceramic resistor across the 5v (red wire and black wire) does the trick. You want to fix that solidly to the metal case, because it will become hot otherwise.

If you have one, you can also use an XBOX 360 external PSU (the grey brick).
Kinda the same, blue+red for power-on, yellows are +12v, blacks are 0v/ground.