Thanks for this info, which I had not seen before, and which every 770 user needs to know. After reading that every boot uses up 25% of the battery's full charge, I made a practice of connecting the charger during reboot. I will stop doing that.

On further reading, I came across some other info which seems relevant to my case of WSOD but not to yours or most other victims'. My case may have been caused not by the flasher utility itself, but by attempting to boot a rootfs with an incompatible kernel.

I had wanted to do something with OS2005 without having to reconfigure the initfs, and therefore tried to flash the rootfs alone.

Yesterday I saw a post by Fanoush (http://talk.maemo.org/showpost.php?p=192475&postcount=2), explaining that OS2006 and the HE's use a different kernel from the earlier OS's, making it impossible to have bootable partitions for OS2005 and OS2008HE on the same machine at the same time. I don't remember any warnings about this in the various guides and wikis for multiple bootable partitions.