Power Mac G5 Firmware Update 5.1.5f2


I have a one-year old single processor (1.6 GHz) PowerMac G5 and this morning the software updater prompted me to install the G5 Firmware Updater 5.1.5f2 (my current firmware version is 5.1.5f0). I followed the instructions, but when I hold the power switch ON as instructed, I never get the flashing power light or the long tone, but instead I got a prompt on my screen asking me to type "mac-boot", which I did and the computer started up but the firmware update never installs.

I've tried several times and the same thing happens. What should I do to install the firmware updater, or do I really need it?

Thanks for your help.