OK, it happened to me, too :-(: My N800 (well, my wife's one at this point , and this forum's people should know why this statement) woke me up in the middle of the night while going in a reboot loop.

No reason, no problem, no previous advices, simply reboot loop!

At the end, everything went fine thanx to the --set-rd-flag/--disable-rd-mode procedure, and now I'm going back to sleep rather peaceful.
The matter is that I have nothing more to add to the bug filed in bugzilla #957, and I didn't think just and only to --set-rd-flag before trying turning on the machine.
I thought that switch on and off the flags should have been enough to reset the consecutive-resets counter as mr. Taaminen explained, but I didn't try to boot with the RD mode on.
What I can say is that the procedure

didn't ended in a succesful boot.

So i flashed the device following exactly the instructions found here and on the list - i.e.

and the device booted on its second try.

After that I disabled the RD mode with
and rebooted with
before disconneting the usb cable, and now it seems everything works fine

Just for the sake of specifying, the device wasn't too hacked: xterm, ssh, horizon and vnc, nothing else (didn't I say that it's my wife's device ?.....)

Conclusions:

• it's a pity that such a device could encounter with such troubles. Why, after all the discussion we had about that and the reason for a whole flash instead a step by step update in case of upgrading of the OS, a software problem couldn't be resolved with a simple flash but needed some tricks? Nokia couldn't expect the joe user to try everything, the flash is the simplest and safest way to repair every software problem. Also members of service center could not be able to repair such a problem and could be tempted to send the device to Nokia main centers, all in all probably they are not members of ITT forum nor Maemo lists
• thanx to everybody who pointed me towards the right direction to unbrick the device.
• I am still in love with these devices, the 770 is the first palm that works for me for more than two months without ending up sinking in some drawer, but... definitely, these problems should not happen! (oh, btw never had this kind of problem with my 770, only a broken display fortunately covered by warranty)