N900 won't boot: gives bright LED/"Nokia" screen for 30 seconds, then quits (likely not a low-battery problem)
*
When I press the power-on button, the LED lights up bright-white,
a brighter-than-usual white "NOKIA" screen displays (with a brief vibration), and both continue for about 30 seconds, then the phone goes dead (this can be repeated).
If I attach the N900 to a car-charger, *the LED glows bright orange and a dim (unlit) "NOKIA" screen displays, both for about 30 seconds (probably with a vibe), then appear to go dead for about 2 seconds, then the dim screen repeats this pattern (the LED behaves variously) indefinitely.
*
Some possible clues:
*
Three times just recently, turning the phone on brought up a bootmenu page, offering 'nand boot' and another boot-choice (this is not something that otherwise appears frequently);

Last week I apt-get-installed wget and debootstrap;
*
About a year ago I had much the same booting problem for a while, except that booting would usually succeed after three or four attempts; the problem eventually went away. I suspected it may have been caused by overcharged batteries (sometimes I charged them externally, but not lately);
;
I charge with a car-charger connected to a 12-volt battery, sometimes in parallel with a 17-volt solar-panel (haven't noticed any problems, except possibly the N900 then charges more slowly);

I download lots of files (mostly htmls with associated folders, pdfs, videos) for offline viewing (malware? ...);

Over the last year or so, as internal and SD memories became fairly full, the N900 has become increasingly sluggish, particularily the Folder app: on pressing a menu button, it can take 15 seconds before there's any visible response.

I'm searching this site and about to try the Flasher, but when I run it, a commandline box shows for a second and disappears. I've seen a simple fix for this but forgot what it is? ...