i had the same problem last night.
i dumped and wrote the nand on a zephyr,to jtag it.
unfortunately,all i get is RROD (0020).if i disconnect the jtag cables,it gives me e79.
so i flashed about 3 different xbr versions,dumped to verify it was wrote ok.
after i flashed another version,the console wouldn't turn on.tried to wrote again the nand,and surprise: "could not detect flash controller".i thought i was fucked,and bricked my console.
then i pluged in the power supply,connected the lpt cable,and started shorting out the pins on the nand flash chip,with a flathead screwdriver.while i was doing this,i sent an erase command in nandpro (nandpro lpt: -e16 0x000000).and voila,it erased the nand,and i was able to write another xbr.bin image.
now it still gives me 0020,but at least it turns on lol.