You need to search for the bin or script /usr/share/acpi-support/power-funcs ,
it may be inside /etc or /lib/lsb/ now or from the DL site of Ubuntu :
The file list is quite large , especially for toshiba and asus .
If you want a rescue CD you can use the 700MB LiveCDs of the various Ubuntus.
It may be the only thing that is hanging your boot , but there may be probably more to come after wards.
If the old kernel worked well with your HW you should keep it .
ACPI can be configured as several modules (button , ac , thermal ...) or inside the kernel .
You don't know if the configuration of the new kernel had changed ,
if you do not diff /boot/config`uname -r`* .