does not power down the system properly

oh, i forgot to mention, reboot works flawless

This appears to get fixed using the test kernel from comment #5 in bug 446140

This bug was fixed in the package linux-fsl-imx51 - 2.6.31-105.14

---------------
linux-fsl-imx51 (2.6.31-105.14) karmic; urgency=low

  [ Andy Whitcroft ]

  * rebase to Ubuntu-2.6.31-14.46
  * [Config] update configs since rebase to Ubuntu-2.6.31-14.46
  * lirc update dropped module lirc_mceusb2

  [ Upstream Kernel Changes ]

  * mxc spi: fix spi driver for 2.6.31
    - LP: #427289, #446140

  [ Ubuntu: 2.6.31-14.46 ]

  * reinstate armel.mk with no flavours
    - LP: #449637
  * [Upstream] elevator: fix fastfail checks to allow merge of readahead
    requests
    - LP: #444915 ...

I have the same problem, but it seems to be a "gdm" problem, not related with acpi nor with "apm"... le te mexplain why:

If i tell it to hybernate it power off at end of it and when powered on again it resumes well.
If i tell it to shutdown it does not power off at end, but hey only if gdm was running when asked.

More detailed:
If gdm is running and i open a terminal window: no way to power off after shutdown, none commands: shutdown, halt --poweroff,... none works
If gdm is running and i press Ctrl+Alt+F2 to go to a console at full screen (text mode), but i let gdm running: no way to power off after shutdown, none commands: shutdown, halt --poweroff,... none works

But, if i press Ctrl+Alt+F2 to go to a console at full screen (text mode), and do:
#sudo /etc/init.d/gdm stop
So gdm is stopped then after few secconds i can confirm it is stopped with [ps -A | grep gdm], so i ask to shutdown with:
#sudo halt --poweroff
Or with shutdown,... all of them at end turns off the power and power off the notebook correctly.

I have seen on Internet a lot of forums on where they tell something about acpi=force, apm=power-off,... on /boot/grub/menu.lst also about adding apm to modules,... etc. none of that works for me.

And i found that if gdm is not running when calling shutdown it power off correctly.

When i was using Ubuntu Intrepid Ibex and Ubuntu Jaunty Jackalope it allways power off correctly, but when i updated to Ubuntu Karmic Koala it starts to not do the final power off when shutdown... now i know the cause is gdm running when calling shutdown.

Maybe it is related in some way with Kernel or with propietary ATI graphics driver...

Also i can see some near identical lines (more than ten) on /var/messages at the end of it with this error:
Kernel: Assertion fail in ../../../../../../../../drivers/2d/lnx/fgl/drm/kernel/hal_rs780.0 at line: 53

I do not know if such error is related with the shutdown problem, but is the last error logged and it is at end ot /var/messages no more lines after it... but i can only see it when not powered off correctly, if i do the trick of stoping gdm it does not appear.

Hope this can help someone to fix-it. Till them i will do the trick of Ctrl+Alt+F2 -> login -> password -> sudo /etc/init.d/gdm stop -> sudo halt --poweroff

Note:
After doing such, i powered on again and then after some hours of work i press shutdown by mistake (did not remember ro do the trick "stop gdm then halt --poweroff") but what surprise! it turns off the notebook correctly... so when i have time i will re-check if it was only once or can be reproduced.

I mean:
-Power On, then tell destop menu to shutdown normally and check if it turns off.
-If not force turn off, then turn on again, do the trick of stopping gdm and halt --poweroff, then power on again then tell destop menu to shutdown normally and check if it turns off.

But i will not have time till weekend, so if any one can also check that, it would be great.

SOLUTION THAT WORKS FOR ME:
Ctrl+Alt+F2 -> Login -> Password -> sudo /etc/init.d/gdm stop -> sudo halt --poweroff

please note that this is a bug about an armel kernel, if you dont see this issue on a babbage imx51 device please open a new bug, you seem to be on an x86 architecture