MacBook insomnia; it doesn't sleep.

Question

My MacBook doesn't go to sleep, unless I press the power button and select Sleep.
Neither in battery mode, nor in AC mode. I tried closing all the opened programs (QuickSilver, Safari, iTunes, iTerm), and put the time to 1 minute to make quick tests. In both AC and battery modes, the screen just goes blank, but the thing is still on (I move the mouse and it's there -- in sleep mode I have to press Space bar or something; I left it there for 7 hours with the blank screen, and the computer was still hot in the morning.... so no sleep).
I run the extended hardware test, and it says everything is OK.
I have had 2 sudden shutdowns this month (always with AC plugged in, computer cold, just turned in, and in 2 or 3 minutes it turns off).
Any idea?

Answer 1

Solution to No sleep after improper shutdown
Re: MacBook insomnia; it doesn't sleep.
(Use any and/or all of these steps at your own risk
(Warning this will erase your osx volume !!!)
Use only If you are very familiar with the Apple Disk
Utility,
I have a possible work around.
This may resolve only the "insomnia" issue and, may
forego the “manual reinstall” of all your
applications, music, document, files, etc..
(this process does take time, but you are making a
valuable backup)
This will not resolve any random powering off issue.
((BTW just reinstalling osx “with the erase first”
option did also fix the insomnia issue on my MBP.
Though I did spend a lot more time reinstalling all
of my app, docs, and geting all the setting just
right)) hopefully the following workaround will be at
very least much more simple than a full reinstall
from scratch.
This work around requires an external backup
hard-drive.
Step 1: First, using Disk Utility Restore(meaning
backup), backup your source "Macintosh" Volume, to an
external hard-disk Volume (destination).
(this, step 1, may take 2-hours+ for ~80GB of data,
via FW400 speeds.)
Step 2: Next, hold "option" while Booting, select
external hard-drive Volume. (the external backup
volume you created in step 1)
(You should now have booted into your mac OSX
external hard-disk backup volume.)
Step 3: From your external macOS volume, use Disk
Utility to erase your "Macintosh" Volume. (the one
inside your Macbook pro ! ).
Step 4: using Disk Utility Restore(now meaning
restore), restore your external backup volume (from
the external Hard-disk source) to destination
internal "Macintosh" volume.
(This, step 4, may take an additional 2-hours+ via
FW400 speeds.)
(Use all and/or any of these steps at your own risk
Good luck.
mbp  
Mac OS X (10.4.7)  
Solution to No sleep after improper shutdown Re: MacBook insomnia; it doesn't sleep.
Re: the previous post.
The insomnia issue is probably caused by an "improper shutdown/power loss".
So this workaround will only be permanent, if you resolve the "random shutdown" issue.
As I think the "random shutdown" issue may be causing the "insomnia" issue.
After a "random shutdown" has occurred, causing "insomnia", the workaround will fix the insomnia. (the make this fix permanent though, the random shutdown must be addressed)
Hope this helps clarify (which one created the other, the chicken vs. the egg)
And gets you, at lease closer, to a full (no random shutdowns and no insomnia) solution.
Take care
mbp   Mac OS X (10.4.7)