Q: After installing mavericks, the iMac will not wake from sleep properly (at all)

Hum.. This discussion is a bummer. Mine was still working fine when I left town Xmas day, so for about four flawless days of 10.9.1. I guess I will find out when I get home!

I downloaded Etrecheck as suggested and it did, indeed, find some rogue items lurking in hidden files, largely to do with MacKeeper (once installed as part of a "megabundle" a few years back and immediately uninstalled without ever using) and SoundFlower (no idea where that came from). I found a utility called "Find Any File" (http://apps.tempel.org/FindAnyFile/) useful to locate these items, incidentally.

Now Etrecheck shows a clean setup, but unfortunately, this still hasn't resolved the problem of not waking from sleep: short bursts of sleep (even a few hours) are fine and the iMac wakes at the press of a key or the click of the Magic Trackpad, but sleeping overnight still causes it to remain sleeping, no matter what I do.

I had thought it might be connected with a change of date somehow, so I tried sleeping the iMac from before midnight until after (a short sleep of perhaps ten minutes), but it awoke just fine then.

Not a lover of MacKeeper. You need to try and remove that and all of its directories asap.   However, Cocktail for 10.9 is very good.  Try that. 

Resetting the PRAM turned out to be a temporary fix - lasted about two or three days, then the issue with not waking from sleep developed again.  I'm currently running 10.9.1 on a mid 2010 iMac.

The only out of the ordinary event that occurred during the time my computer was behaving was installing a new version of the software for my Brother scanner/printer.  The problem appeared immediately following the new software installation.  This may be just a coincidence.

Last night I decided to switch off sleep mode on my iMac altogether using system preferences.  The system went to sleep and would not wake in the morning. 

That sounds odd if I am understanding it correctly AW1960.  Are you saying you turned sleep off by sliding all the settings in Energy Saver Preferences all the way to the right (to "Never"), and then later the machine went to sleep?  That should not happen.  Never means never.  Did you put the machine to sleep manually - likely from the Apple menu?  I suspect manualy going into sleep would be the same as having it happen automatically - the issue seems to be that once the machine is sleeping something gets in the way of letting it wake.

But, maybe something else happened (e.g. something unrelated to this issue), or maybe I am just misunderstanding what you said.

Thinking about this and trying find clues sifting through the logs with Console a couple of things to consider come to mind.  Most of the reports here seem to link the appearance of the will-not-wake problem to the installation of 10.9.  What changed in 10.9?  One thing was that multiple displays are handled differently than before - the menu bar and the dock can move between screens now, and the screens can have different Spaces, depending on settings for example.  I am working on an iMac with its own screen plus two more monitors - total of three screens.

It certainly seems possible that some app, etc. is not quite ready to deal with something in the new features.  It seems to me the problem is most likely that some more or less random combination of the events that are always going on behind the scenes, even during sleep, occasionally hits a situation that results in a hang somewhere in the display support parts of the system that keeps it from being able to receive or process a wake request.

So, observations about seeing the problem on single vs multiple monitors, and the fairly obscure setting in Mission Control Preferences to have or not have separate Spaces per display might be useful.

You've interprete the situation correctly.  I used the energy saver menu in system preferences to set the computer not to sleep.  I left the computer for a couple of hours and it went to sleep automatically at some point.   It then would not wake (after several hours asleep), resulting in my having to power off and on again to use the iMac.  I've since set the sleep settings in energy saver back to their default values.

Hmm, that seems odd. I don't know of a way for it to sleep if the Energy Saver prefs (both display and the CPU) are set to never sleep except, maybe to manually do a sleep.

Are you sure it was sleeping?  Any chance it was actually shut down or in some other state with dark screen(s)?  For example a brief power glitch can cause a machine to shut down and it will stay off if you don't have start after power faIlure set.

If you use Console you can look at the logs to get some idea of what happened and when.  Not easy but maybe a clue there.

I said " I don't know of a way for it to sleep if the Energy Saver prefs (both display and the CPU) are set to never sleep except, maybe to manually do a sleep."  Actually there is at least one more possibility.  Off the Energy Saver Prefs window you have a function that will schedule Sleeps and shutdowns and wakes and so on.  A scheduled Sleep could be set up there and it would override the Never sleep settings on the main window at the designated time.

I agree - I wouldnt have expected it to go to sleep but the screen switched off and the system was unresponsive when I woke it, the same as when the default sleep settings were in plaace.

This problem with not waking the computer seems to be quite strange:

When I attempt to login, the iMac screen comes on with a mouse click, I can enter a password using the keyboard and when I press return to login I hear disk activity but the login screen remains in place until the screen goes blank again (about 15 minutes). 

While the screen is on, the clock in the top right of the screen advances normally.

I see notifications in the top right of the screen from Facebook, Mail etc.

If I am streaming a movie to Apple TV, it seems to stream if the movie starts when the computer is awake, but after it goes to sleep I can't play a new (different) movie (I get a content unavailable message from Apple TV) - I guess that movies get bufferred to the Apple TV itself).

On restarting, after logging in, Itunes will have lost its Home Sharing settings (Apple TV says that home sharing is not turned on, iTunes says it is turned on, and it has to be turned off and on again for other devices to be able to share content).

I reported all of this to Apple and was told by the technician that the problem was by Bluetooth mouse and keyboard not connecting which isn't correct as I am able to bring up the login screen and enter my password.  The problem doesn't appear to have made it to the Apple support knowledgebase yet.

As Alice once remarked, "Curiouser and curiouser."

I have removed all USB-connected externals, leaving now just the Ethernet connection to my router; I have checked with EtreCheck and removed the few offending items, so I have a supposedly clean system (though I admit to the folloing extensions: FlashPlayer, Flip4Mac, Java, MacFUSE, VLC Streamer). I still have problems waking from sleep, however: my iMac almost never wakens after a night's sleep, preferring to stay with a black screen even though the hard drive is running, and will occasionally, though rarely, refuse to awaken fully during the day, though then choosing to open to a white screen!

I have also tried setting a scheduled wake-up through Energy Saver. I scheduled this to wake up at 10 o'clock in the morning; this morning the iMac awoke at approximately eight-thirty; at least it woke up! And, yes, the system clock is correct.

I spent some time on the phone with an Apple support tech this afternoon.  We  verified the internal disk, checked and reset the file permissions, reset the PRAM and then set the computer not to sleep (again).  So far, the computer has not gone to sleep (like it did a few days ago).  The technician was of the opinion that Mavericks requires a clean install - there have been problems with upgrades.  I'd be interested if those experiencing problems installed Mavericks from scratch or applied the upgrade delivered via the App Store (which is what I did).

The next step is to do a clean install and restore data from Time Machine.

I have been fighting the wake from sleep issue since the morning after I installed Mavaricks.  Two days ago I took the mac mini to the Apple Store for that and a problem with my usb 3.0 ports shutting off.  I kept getting an error message stating that:  Your USB devices have been disabled.  Please unplug the device that is using too much poewer to re-enable your USB ports."  Not an exact quote, but you get the idea.  That happened right after installing Mavericks as well.  Same devices as before.  Another "head scratching" moment... or Hmmmmmmmmm.

I will repost whatever solution the Genius Bar guys come up with for my case.  I was actually hoping to have heard from them by now.  I am writing this post from my Windows 7 / i5 powered HP work laptop.  By the way, it is an i5 with 8 GB RAM and has been blowing my i7 with 16 GB of RAM Mac Mini away as far as performance goes!  I would not be surprised to find out my Mac Mini has other problems than just the Mavercicks related not being able to wake from sleep problem.