Sleep mode doesn't wake up

It just does happen randomly from time to time.
At the company im working for, the users just go out for lunch and comes back later, pretty much like any company.
Of course the computer probably went to sleep and then when they try moving the cusor, it apear on the screen "saving your settings".
Then we have no choice to shutdown the computer manualy and reboot it.
Were running on Windows XP Pro SP2

heres some of the following computer:

NETVISTA M42 2.5 Ghz 8305-61U
NETVISTA M42 2.6 Ghz 8305-81U
THINKCENTRE M50 2.66 Ghz 8187-D1U
THINKCENTRE M50 2.8 Ghz 8187-E4U
THINKCENTRE M50 2.8 Ghz 8187-SAU
THINKCENTRE M51 3 Ghz 8141-23U
THINKCENTRE M52 3 Ghz 8212-1QU
THINKCENTRE M55e PD/2.8 Ghz 9632-D6U
THINKCENTRE M55e C2D/1.8 9632-Q2U
THINKCENTRE M57 C2D/2.33 9181-A1U/A1F

I also had a similar issue for some Dual Core Laptop from lenovo in an other company. Well instead of showing something in the screen it was simply staying as black as it was...
I know it was the chipset driver and the patch was the q2vdo27us13 file.

It apear that many people are having some Sleeping/Hibernating issue in here... Well as i can see, theres several post. I dunno if its a general bug or its issues that aren't related...

Thank you in advance

I've checked the power alimentation and everything is set to do nothing... except closing the monitor after 5 minutes

Altough i might think that Windows Update could be part of the problem there.

Someone reported me the problem today
It was saying "Saving your settings" as the session was trying to close, it just keep on the message like an infinite loop

In the event viewer i could see that
Microsoft .NET Framework 2.0 Service Pack 1 (KB110806)
was ready to be install

Would that program be bright enought to say that because the user isn't there, install itself and then start a reboot since needed for that kind of update?

The Updates are set to "Automaticaly download and install" but it will run the installation at 03h00 AM...altough, the session "shuthing down" happened somewhere between 12h30 and 14h15

Thanks for the suggestion altough, i'm not on my home computer... its a company that has more than 600 users... and this kind of problem isn't always happening ...perhaps 2 times per week ....on those 600 users... so theres no way realy to know for sur....

Plus, we can't just stop downloading updates...
All the updates are schedule to be done Friday morning at 3 am...any of them... and this kind of problem is from a long time ago....so it wouldnt be just this update if so.... but perhaps updates that require reboot...that could be possible

but i find funny the guy that posted this in this forum
"http://channel9.msdn.com/ShowPost.aspx?PostID=318985"

"Sometimes it's still funnier… it's Tuesday morning, so Windows install the latest patches. It will start annoying you about: 'I need to restart'. You keep saying no because you are busy.
Two hours later you can relax a bit, so you go for a coffee. You found people over there and chat a little with them, so 30 minutes later you are back on your desk just to discover Windows has decided by its own will it was a good time to reboot (because you didn't say no the last time it asked)… of course, you didn't save that document."

Hi

yes, thats how it works... i don't know much how cause im not in charge of that part and i'm quiet new here ... Altough i know theres a server that manage the propagation
Still on the user settings, it says that the update gotta be done at 3 am friday ... but the file is beiing transfert way before to the computer

Sorry if i forgot to give you this information