I just made a fresh new install of whezzy (7.0) on an old computer (P2 233 and 256MB Ram, yes a monster for cups it's more than enough

The shutdown was working on a Sarge or Lenny, but neither with Squeeze nor Wheezy.
With the "old" debian's I had to add a noacpi flag in grub, but with Squeeze it wasn't working anymore.
When i use the halt (or shutdown) command I have at the end
[info] Will now halt.
ata2.01: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x0
ata2.01: failed command: STANDBY IMMEDIATE
ata2.01: cmd e0/00:00:00:00:00/00:00:00:00:00/b0 tag 0
res 51/04:00:00:00:00/00:00:00:00:00/b0 Emask 0x1 (device error)
ata2.01: status: [ DRDY ERR ]
ata2.01: error: [ ABRT ]
System halted.
and that's all... the computer stays like that, no shutdown no power off.
I have to press the power button to shut him off...
Any Ideas ?
thx in advance.