Sony has only released one BIOS upgrade for my laptop model and it is for Windows only, it starts the upgrade in windows, then restarts and finishes there.
That's quite a mess Sony has made for you . I'm surprised that they don't have a bootable floppy based update since I've heard that doing it from the hard drive is really dangerous (not sure why, but that's what I've heard). I assume that you don't have a Windows partition anywhere that you could run it from. I suppose you could try running it from Wine, but I would tend to think that that could cause problems.
I don't remember for sure, but I think there's a kernel option like acpi=force. If your BIOS really is broken, there might be some stuff that won't work, but hopefully the poweroff would. HTH.
you might want to try the latest acpi patch for your kernel.
i had problems on my laptop with the acpi stuff that shipped with the kernel i had. after i dowloaded the latest patch and re-compiled it worked well after that.
info on acpi in linux: http://acpi.sourceforge.net/index.html
Sorry I disappeared for a while. I was stuck on dial-up at home and it's a pain because we don't have two phone lines. Back at school and my network connection now though
Make sure that you install the acpi packages in 10.0. IIRC, they aren't automatically selected by the installer, so I think I had to select them automatically. That could be why it can't find the acpi daemon.