well, I just went through another problem. the rootfs on my SDHC card was somewhat corrupted. /home directory got messed up and gone, I booted off the flash(my rescue rootfs), and run fsck on it, then copy the home directory from the flash over, and re-run the restore software, and it's working again.
On an unrelated note, my n800 unit is can no longer connected to my computer via USB. Well, that's not entirely accurate. I still can flash the device, but once booted normally, my computer cannot see it. 2 of my computers cannot see it using 2 difference cable, and my laptop which dualboot winXP/kubuntu don't see it either in both OS. On linux, I don't even see my n800 as /dev/sd*. I tried difference kernel, and no help. I tried booted off the flash, no help. Of course I didn't tried all the combination. But that's not the point. My SD rootfs is my productive is obviously no longer working properly.