With any computer problems can arise, including Mac. Actually one of the most common incidents in this case is the failure of the computer from sleep. We have to shut down and re-include the Mac, so, they say, bring it to life. As in any situation, there are reasons, and to understand them, you can easily get rid of the problem. Let's look at these reasons.
Firstly, sometimes peripheral device like a printer or external hard drive connected to the Mac via a FireWire or USB port, provoking the problem. In this case, you must make sure that the computer freely in and out of sleep mode when the periphery. Problem solved? Well, it is necessary to turn off all third-party devices before the Mac once again go to sleep.
Secondly, it is important to make sure that on the OS X install all software updates and patches. Furthermore, the Mac can not afford to «wake up" and hung or unstable third-party programs. To determine the cause of this kind, it is necessary to check the system log after the incident (done using the "Console" system application).
Finally, if these tips do not solve the problem, then it might be a problem with the inside of OS X (broken files, the problem driver, the old "tails"). In this case, the release of the operating system will reinstall when you save a backup of all data. By the way, as an option to determine that the failure to blame for some third-party software or settings - to create a new user on the system and try for some time to work in this account. Also, do not rule out hardware problems, even though they usually do not cause difficulties with access to a PC from sleep mode. On the other hand, if suddenly something happened with RAM (broken cell) or "fray» HDD / SSD, then there may be all sorts of "glitches".