Just one comment on this.
I also had some troubles rebooting. Most of the times I needed a reboot it took-me several steps in order to bring the phone up again.
I always pointed this issue to KP and overcloking settings as when the phone booted the message "your kernel setting where not loaded due to unespected reboot. loaded default settings..blabla bla".
Some days ago I steped into this thread...
Cheked my version and surprise...

Nokia-N900:~# dpkg -l | grep -i libxau6
ii libxau6 2:1.0.6-1-meego1141+0m6 X11 authorisation library


Did the downgrade...

Nokia-N900:/home/user/ugames# dpkg -i libxau6_1.0.3-2osso1.1_armel.deb
dpkg - warning: downgrading libxau6 from 2:1.0.6-1-meego1141+0m6 to 1:1.0.3-2osso1.1.
(Reading database ... 48753 files and directories currently installed.)
Preparing to replace libxau6 2:1.0.6-1-meego1141+0m6 (using libxau6_1.0.3-2osso1.1_armel.deb) ...
Unpacking replacement libxau6 ...
Setting up libxau6 (1:1.0.3-2osso1.1) ...
Nokia-N900:/home/user/ugames# reboot now
Nokia-N900:/home/user/ugames# + [ x6 = x-t ]

Perfect reboot this time. Quite different from previous ones.

Going back to previous situation (reboot loops/problems), this is what I used to do before today.
1. Reboot the phone via shutdown / reboot commands or just by pressing the top button.
2. When the boot process begins and the phone started to loop in the boot sequence or just did not boot up (don't even see the progress dots). - shut it down and remove the battery
Reinsert the battery and turn on the phone, after the 2nd boot attemp the phone was up again.


Just performed 2 consecutive reboots and no loops occurred , and the phone boots up nicelly.
Thanks. and hope my experiance also helps someone not to reflash the phone.