I was upset to find that Vista doesn't activate hibernate by default, but a little bit of googling will tell you how to turn it on.

Unfortunately, about half the time when I tell my computer to hibernate, it will immediately wake back up right after shutting itself off. It's a Dell Vostro 400.

Has anybody heard of this behavior? Better yet, is there a solution?

I have seen this happen on my ThinkPad running XP (the immediate resume from Hibernate). I would assume it might be related to some "Wake On ..." setting I have enabled in BIOS, but I haven't spent the time figuring it out...

I checked for "wake on" stuff in my BIOS and made sure everything was turned off.
Didn't help.

Don't know if the issue and solution listed below will work, but it may be worth as shot:
http://blog.leekelleher.com/2008/03/22/vis...ation-problems/

What happens if you let the computer hibernate on its own?

Same thing. Sometimes it works. Sometimes it's still running when I wake up the next morning.

Do you use a wireless mouse, keyboard or other wireless device connected to the computer? I had a situation in an office where there was alot of radio interference. The mouse pointer would wander around by itself and at various times random characters would appear when working on documents. Connecting a wired keyboard & mouse corrected the issue.

I'm just wondering if any wireless device is picking up a signal from an outside source & waking the computer.

Keyboard, mouse, and ethernet are all wired.

I've also tried quitting all running programs before hibernating and have still had the problem.

It just happened again, so I fired up event viewer.

4:59:58: I see a Kernel-Power message saying "The system is entering sleep".

5:00:52 Then I see a "Tcpip" message saying "The system detected that network adapter Local Area Connection was connected to the network, and has initiated normal operation."

5:00:54 Then I see a "Service Control Manager Eventlog Provider" message saying "The Windows Image Acquisition (WIA) service entered the running state".

5:00:55 Then I see a "Power-Troubleshooter" message saying "The system has returned from sleep". It also says "Source: unknown".

So, does this sound like a wake-on-lan issue?

Try disconnecting the network cable &/or disable the network adapter and see if it hibernates.

If it is, and if it's not a feature you need, see if you can disable WOL in BIOS.

I went into device manager and found a setting for the network adapter: "Wake on Directed Packet".

I hope that's it.