Must click "sleep" twice to make computer standby?

When I'm finished for the day, I will manually go to Apple | Sleep... Most of the time my iMac will sleep momentarily and then immediately re-awake! Usually, on the second "try" the "sleep" holds.

If anyone has a solution, I'd appreciate hearing what it is.

I have had the intermittent "need to put to sleep twice" issue since my very recent 10.6.5 upgrade. For me, the problem seems to be an external disk drive that refuses to sleep right away and/or a hard drive from another iMac mounted over the network. (My keyboard and mouse are wired.)

One thing I tried beyond what is listed in the below help files is to go to Spotlight Privacy in System Preferences and turn off indexing for my external and network drives. (For example, indexing backup disks seems wasteful to me.) It's tricky to declare success since the problem is intermittent.

Try reading these:

* "If your Mac computer won’t go to sleep or stay in sleep"
http://docs.info.apple.com/article.html?path=Mac/10.6/en/9040.html

* "Mac OS X: Why your Mac might not sleep or stay in sleep mode"
http://support.apple.com/kb/HT1776

@nobutan: Understood, my reply was directed to nkh.

When you say "clicked on the sleep button" do you mean you select the Apple Menu->Sleep item or you press your Macbook Pro's power switch and select the Sleep button in the resulting dialog box?

-Steve

did you give it some times? depending on the applications running it might take a little for the machine to sleep. click on sleep, then give it a minute or something, see if it really doesn't do anything.

is automatic sleep after a set period working for you?

I have the same problem. The first sleep wakes almost immediately the 2nd holds. Does not matter how I start sleep (form menu, keyboard shortcut, or hitting power button). Have not really investigated it myself.

applark,

You are right!!! I have two drives hanging off my iMac:
a USB one and a Firewire one.

If I unmount the USB drive the computer goes to sleep without problem every time.

Thanks ... that was it!!!

For those with this sleep problem, do you have the Enter Saver preference for "Wake for network access" checked? If so, you might try turning that off. It's been a while now, but I remember having this double sleep problem too, plus my machine waking up for no obvious reason. I turned off that preference and sleeping behaves ok. I think in my case it was due to a weather program that updates it's weather data periodically from a web site.

@nkh: You have a Bluetooth Mighty Mouse, correct?

Try removing the batteries to turn if off. Does your problem persist?

If not, then replace the batteries. Did the problem disappear?

-Steve

I have the same problem but no external devices at all.

That solved it for me. I had the "Wake for network access " checked. That would explain the random waking and the put to sleep twice problem.

Thank you for your suggestion/solution!