Apple keyboard or mouse won't wake up iMac from sleep.

I had this problem with my iMac and my Dad's iMac occasionally not waking up from sleep without using power button to shut down and restart

i have been running Mac OS X Lion since the day it came out and this problem has not happened once since. I still have my fingers crossed, but so far, so good.

funny. this problem didn't start for me until i switched to Lion.

3 months have gone by under Lion and wake up problem never came back

I'm having the same issue. I thought it was a bluetooth issue so I went and grabbed the original USB keyboard and plugged it in and it still didn't work.

From what I have seen this problem only started recently with this last software update, and there was at least one more thread about this same topic.

I'm on 10.7.2 and the problem just started about 5 days ago.

hi - did you find an answer to your problem, I had exactly the same problem after installing Lion. I decided to do the simplest thing first - went to system preferences/bluetooth then highlighted each device one by one, then unpaired them and re-paired them - hey presto it worked[for me anyway] Good luck

unfortunately i tried that. i plugged my old keyboard in via USB, unchecked everything, then did just what you did. It worked for a couple days but then the problem started again. At this point I'm not sure if i should take the computer into Apple or wait for a software update. it is very annoying, though. I'm happy it worked out for you, though.

i meant my old mouse, not my old keyboard.

everyone having this problem, please examine your area where the MAC device is located. I read on this thread where a person had a problem with their iMac running hot and that was their cause for not waking after sleep. after investigating, my mac was definitely hot to the touch at the back & top area and it was sitting pushed back as far as it could go on my desk where I guess it was not getting enough ventilation. I have since moved it out 2 inches so the top vent is not covered and I'm now going on 4 days with no problems waking from sleep. before I had to power it off/on 3-4 time per day. it worked for me so please investigate a possible over heating issue before restoring your hard drives and replacing your devices.

good luck and hopefully this simple solution works for many of you.

My work computer, the iMac having the wake from sleep issue, does run hot, but there are no walls (or anything else) near it to block ventillation. My iMac at home does not run hot and has no problems waking from sleep.

The work computer went in for testing in late February. They could not replicate the problems I was having.

I just had an Apple-certified repair shop replace my Bluetooth radio but am still having the same problem. Also, no ventilation issues as my computer has plenty of air around it. I'm wondering what my options are now that's it been "repaired?"

unfortunately my sleep issue returned. I thought I was on to something with the heat as I didnt have it lock up for 4 days.

I think until Apple takes this seriously and finds the true root cause, we'll have to keep speculating and trying anything for a remedy.