Simple instructions for restoring the Factory Firmware...
In order to keep these instructions simple, I'm going to make some assumptions:
You've already got linux running on your desktop PC (I've not tried these instructions in VMWare or VirtualBox, but using a LiveCD should work fine)
You've got sudo working (allowing you to run commands as root)
You've made a backup of any important data in your Bifferboard's flash (cos it's gonna be wiped)
You've not changed the biffboot command line (if you have, set it to an empty string before following these instructions)
You've checked that biffboot kernelmax is set to 0x10 (if not, reset it in biffboot)
You're using an 8MB-flash bifferboard, and you're using Ethernet flashing (and you've not disabled your bifferboard's network console in biffboot)
You don't blame me if everything goes horribly wrong!
Step by step instructions
Create a temp directory, and change into it: cd $(mktemp -d)
Download the firmware image: wget "https://sites.google.com/site/bifferboard/Home/factory-firmware/openwrt-rdc-jffs2-64k-bifferboard.img?attredirects=0&d=1" -O openwrt-rdc-jffs2-64k-bifferboard.img
Connect your bifferboard to your network, but don't connect power yet
Flash the kernel to your bifferboard using the appropriate upload script: sudo python bb_eth_upload8.py eth0 01:02:03:04:05:06 openwrt-rdc-jffs2-64k-bifferboard.img (you'll need to change the MAC address for the one on your bifferboard, and then plug in power to the bifferboard when the script tells you)
Hopefully it'll all go okay, but I've had instances in the past where it doesn't work first time. If this happens to you, unplug your bifferboard from the power and repeat the previous step.
It'll take a while, but eventually it should get up to "Written chunk at 445"
Leave your bifferboard plugged in - the first full boot takes about 5 minutes (it initializes the flash-filesystem, and then generates unique cryptograhpic keys for use by the SSH server). Subsequent boots take about 45 seconds.
Look in your router's dhcp logs to find out which IP address got assigned to your bifferboard
Connect to your bifferboard's IP address with telnet: telnet 192.168.0.56 (your IP address is likely to be different!)
Connecting with telnet automatically logs you in as root, with no password. Note the "IMPORTANT" text displayed at the top of the screen to enable SSH.
After running "opkg update" you can install extra packages by using the opkg command, until you run out of Flash space ;-)
You can also play with the "LuCI" webinterface by going to http://192.168.0.56 in a web-browser