My mac often doesn't respond after sleep mode. What can be the reason?

There are a lot of articles about what to do in this situation. But I can find nothing about how to Prevent it.

Mac is macbook Air. OS is OSx 10.7.4

  • Do the screen light up so you can see the desktop or is it just keyboard that light up and screen keeps black? – Hoshts Aug 17 '12 at 22:06
  • Different things. One time it showed all windows and shows colored circle instead of mouse. Few times it was black screen with such a circle. Few times - just black screen. – klm123 Aug 17 '12 at 22:07
  • Does the computer ever crash and ask you to reboot it? Reason I ask is that I had kind of the same problem with my MacBook Pro in Lion. In addition I had the problem that it crashed and wanted me to reboot after random time of waking up after sleep. – Hoshts Aug 17 '12 at 22:11
  • he never asked.:) I just had to do this having no other option – klm123 Aug 17 '12 at 22:17
  • How did you fix the problem? – klm123 Aug 17 '12 at 22:17

I had the same issue on my mini. The first thing you might try is resetting your PRAM and then your PMU. These control sleep on your mac. If they fix it, and it goes bad again, you may need to take it in for warranty repair (if under warranty.)

  • I tried reset PRAM many times - no changes. There is no PMU on laptops, is it? – klm123 Aug 19 '12 at 17:42
  • I think PMU is related to older laptops. If none of those things fixed it, you could try waiting for the next version of the OS (lest it’s an OS issue) or try a clean install (you have a Time Machine backup, right?) But it’s probably a trip to the Genius Bar for you. Good Luck! – Greg Cain Aug 20 '12 at 17:59

Looks like I fixed it. The problem was, that I divided my disk onto three logical disks. And system was confused, which one to be used for booting. When I chose Startup Disk in System preferences (even though there was only one option) the laptop wakes up normally. (I had no problems during three days)

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