Mac address is invalid in both cmos and flash

does your mac have a battery back up battery like pc's do.
the battery in the mac may not have enough power to keep the cmos information together, replace the battery and you should be okay

i have your problem.but when i use asrock mac tool it said "Not supported"!.infact it not supported mac address on stick on main board!but my hope was the mac 6 digit that newer tool write.then i change my mac by mac changer from windows and then set that mac to bois and flash by asrock mac tool.every thing get ok:)

reinstalling your os has nothing to do with bios, you are getting this message long before any hard disks are involved in fact the bios doesnt even have the interrupts running for the USB devices at this point, you'll notice this if you have a USB keyboard. The only possible solution is to flash or replace your BIOS chip - this is a LAST RESORT option. I dont recommend it if the system works other than the LAN. Your best solution is to install a network card in a free PCI slot, they are pretty cheap if you know where to look, heck even goodwill carries them in their 1$ computer junk bin thats where i bought a few of my 100baset cards (of course at your own risk) hope it helps

The MAC is the unique identifier for the onboard LAN chip - if it's invalid then the chip has been fried - disable it from the BIOS and install a new PCI LAN card.

The onboard LAN chip has been fried. Disable it from the BIOS and install a separate PCI LAN card.

Find the highest version bios flash file 1.50 and do it from DOS from a Boot Floppy or CD

http://www.asrock.com/mb/download.asp?Model=775VM800&o=BIOS

configured the BIOS settings yet? Make sure your set the RAM to run as Supports DDR400/333/266 non-ECC, un-buffered memory Max. capacity of system memory: 2GB
the RAM you installed and to match the CPU bus. And there's probably several other settings that need to be tweaked as well. For example, if you're not running RAID, disable it.
If the problems continue, you may wanna try updating the BIOS. Actually, I just had a look at the ASRock site & here's what the latest BIOS fixes: "Modify MAC address function algorithm"

http://www.asrock.com/mb/download.asp?Model=K7NF2-RAID&s=462

MAC address is not held in CMOS. Please describe the symptoms - what hapens when you switch on, what does message say exactly?

K, i hv a solution for u, first u need to download afudos utility from http://www.ami.com/support/downloadagreement.cfm?DLFile=support/downloads/amiflash.zip&InpDrvID=90. And then go to DOS mode, n type command like,
D:\...........\afudos /mxxxxxxxxxxxx
There is /m is the command n 12 times x is ur mac ID. N u can find ur MAC on some were on ur MB.
I think this will fix ur problem.

run cmos setup and try to configured in factory default settings...