Hi all!
I'm having a problem here - my N900 won't boot, and this is not even the main issue
First, I just noticed that for some reason my device was in 'flight-mode', and when I tried to put it back on its normal mode, it began to behave weird so I decided to reboot it.
Since then, it won't boot anymore - when pressing the power key it vibrates but gets as far as the "Nokia" screen, then it stalls for ~30 secs, and then the display dims off slowly until its completely turned off.

Long before this odd thing occurred, I installed BackupMenu V2 and backed up my entire system successfully - but even if I try to power the device with the keyboard open, BackupMenu won't start.

Now, is it possible to access the device's file system in flashing mode? I can get there and I already reflashed my firmware but the device would still not boot (not eMMC yet). I also tried activating R&D mode, but the device is still acting the same way as before (going as far as the "Nokia" screen and then slowly dims off), only of course while having the R&D icon below the 'Nokia' logo...

I don't know if it has anything to do with it, but my device was overclocked (930Mhz + 500 dsp) for quite a long time before today...

Any help - as usual - is highly appreciated

It's a longshot, but since you're already re-flashing...
Pull the battery out (with it off) and wait at least 10 seconds.
Put the battery back in, then re-flash (not emmc) and wait for it to do what looks like an attempted reboot.
Pull the battery out again (and wait again).
Hopefully it'll power back up after this.

It didn't work, but thanks nonetheless

If you can flash to PR1.1, I think that also gives you USB mass storage mode. I'm not sure it will work for you considering you already put it into R&D mode, but I suppose it might be worth a try.

Is the battery charging properly? It might be worth charging it up in any old compatible Nokia you might have lying around.

Boot into rescue kernel and activate USB mode. details on booting the rescue kernel are in the wiki on the page about repartitioning the emmc. It is under the section on custom partition sizes.

IT WORKED! Thanks man! I got into USB mode and backed up my /MyDocs, but now for some reason I can't use the flasher to flash the eMMC - when I connect my device in flashing mode and start the flasher, the flasher recognizes the device and tries to boot it into flash mode, but then the device immediately 'disconnects', I don't know why.
I tried using the flasher to disable R&D mode by simply running "flasher-3.5 --disable-rd-mode" and the command was executed successfully, but still the device disconnects when the flasher tries to boot it into flash mode...
Thats odd, since I've flashed my device numerous times and this never happened... Maybe there is a need to flash a different kernel into it first, to replace the rescue kernel?

UPDATE: I've finally accomplished to successfully flash my eMMC and firmware. It appears that after leaving the device connected to the USB for a minute or so, after it looses the connection with the flasher while trying to boot the device into flash mode (as was described above), the device suddenly boots up again, going all the way to the maemo's "5 running dots" load screen, which freeze after a few seconds.
Flashing the eMMC is able to work when the dots freezes, so I successfully flashed my eMMC and then turned on to flash the device's firmware, which also went fine (it appears that the flasher won't 'lose' the connection with the device when flashing the firmware, as opposed to flashing the eMMC).
But yet, the device won't boot.
If I turn it on, it'll just do what I described in my first post on this thread (e.g going all the way to the screen with "Nokia" logo and white background, and then the screen fades out and the device is turned off).
If I connect it to the USB, it starts immediately as if I started it in flash mode (like I pressed 'u' when I connected it - which I didn't press), then quickly leaves flashing mode, stays lit for a few moments and then the screen fades out and the device is turned off - only now it does that in a loop, even if connected to the wall charger.

Any ideas anyone? Is my device finally dead?

I am not sure what you are doing but you need to flash emmc without -R (reboot)

1. Flash eMMC.
2. On success, take out the battery.
3. Setup flasher to flash kernel, leave at 'waiting for USB device prompt'
4. With usb plugged in, insert your battery and wait.
5. The flasher should find the n900 then flash.
6. Reboot.

I dont think you have broken your device. Imagine if you will a civillian in tattered combat fatigues; bloodied, broken, 117 days dying and not quite dead surrounded by the devastation of a thermonuclear wasteland. He is the last of his species,endlessly stabbing an N900 with a shard of glass oblivious to the blood pouring from his hand. All the while he is weeping in a tone that would curdle a heathen god "die n900 die, why can't you die?!"

A man of your punative strength alone cannot break an n900! You just need to get the magic flashing sequence right.

My first reflash took around 5 attempts!

Thanks vi_, but as I mentioned - I flashed my device numerous times before - including the eMMC - and I know I shouldn't use the '-R' option when flashing the eMMC so of course I didn't
The steps you mentioned, from 1 to 6 - thats EXACTLY what I did (since I've never had this problem I described in my first post here, I just wanted to make sure I'll take no chances this time) and everything worked great - and yet, the results are laying in front of you - my device won't boot

P.s, when you write "3. Setup flasher to flash kernel, leave at 'waiting for USB device prompt'", by "flash kernel" you mean flash the firmware, right?

Yes, at step 3 I meant firmware. All I was trying to imply was that flashing is a black art.

FOr example I never had to press and hold 'U' to get the flash to work, however I did have to take the battery out between eMMC and fiasco image flashing.

From your description of things , flashing at the screen with 5 dots(?) sounds totally nuts. I would try flashing again without said madness.