So, see post #4 in this topic.....and let me know how you get on.....
You can also extract your original DSDT.aml file off the PC using the Ubuntu Live DVD, plug in a FAT32 formatted USB flash drive and then go to the Terminal and type either
cd /media/"Volume name of the USB flash drive" sudo cat /sys/firmware/acpi/tables/DSDT > DSDT.aml
for Ubuntu 11.xx and later, or
cd /media/"Volume name of the USB flash drive" sudo cat /proc/acpi/dsdt > DSDT.aml
for Ubuntu 10.xx or earlier
In either case, the extracted DSDT.aml file should have been saved on the USB flash drive, for later decompiling, patching and recompiling using iasl or iasl based tools.