The common issues that Macs suffer from are often very easy to resolve. It'll be worth your time to try the quick fix before you call in a professional technician, but if it doesn't work, feel free to reach out to MC Services for professional Mac repair and Mac consulting.
Disk permissions are a set of access rights for each file and folder. So if you're on your Mac account, you won't be able to view files of any other user account. To repair misbehaving disk permissions, use the Disk Utility application found in your Applications → Utilities folders. However, this won't fix all file permissions, only the Apple OS-related ones.
Once you open up Disk Utility, select your startup disk (should be the first listed) and click on Repair Permissions. This can fix a variety of issues including the following:
Often times, an issue can be fixed by merely updating software. These updates are critical to the function of your device, but it's a good idea to wait about two weeks before installing if you can put it off. However, software updates aren't only limited to Apple software and OS X. There are tons of software that require individual updating.
OS X Mountain Lion
To update, open the Mac App Store using your Apple menu on the top left corner and select Updates. Anything purchased from the App Store and your system will update if available.
OS X Lion and Below
Use the same App Store method to update any third-party apps.
If you've noticed that some apps won't run successfully or can't open using Software Update or the App Store, you should use Terminal.
Display the list of available updates by typing in the command sudo softwareupdate -1 and to install the updates, use the command sudo software update -ia.