Try some basic troubleshooting.....
REPAIRING DISK PERMISSIONS -
NOTE: refer to article "About Disk Utility's Repair Disk Permissions feature" found herehttp://support.apple.com/kb/ht1452 - for the actual apple article on these step. ----
- click finder in the bottom dock, and in the window that opens, select applications in the left column - scroll through until you see the 'Utilities' folder and double click to open it. Then double click on 'Disk Utility'
- When prompted to select a disk volume or image, select the 'Macintosh HD' in the left column
- ensure the the "first aid" tab is highlighted blue in the middle of the screen
- click the button at the bottom that says 'Repair Disk Permissions'
- this process will take a few minutes to run. It will indicate it's done, by scrolling to the bottom of the "details area" displaying 'Permissions repair complete'
Dan Frankes has written an excellent article for Macworld on "Permissions" and the need to repair them - see - http://www.macworld.com/article/52220/2006/08/repairpermissions.html. Another good web site is - http://www.thexlab.com/faqs/durepairfns.html.
REPAIRING DISK - About OS X Recovery - http://support.apple.com/kb/HT4718.
- restart your computer hold down command + R keys on the keyboard to boot you into Lion / Mountain Lion Recovery mode
- select english as your main language then the continue arrow
- select "Disk Utility" on the resulting screen then 'Disk Utility' ---
- When prompted to select a disk volume or image, select the 'Macintosh HD' in the left column
- ensure the the "first aid" tab is highlighted blue in the middle of the screen
- click the button at the bottom that says 'REPAIR DISK' .......NOT "Repair disk permissions"
- this process will take a few minutes to run. It will indicate it's done, by scrolling to the bottom of the "details area" displaying "The Macintosh HD appears OK"
If you get any other message OTHER than "The Macintosh HD appears OK", like "the Macintosh HD was repaired successfully" run the "Disk Repair" again, until it displays "The Macintosh HD appears OK".
Once done, restart the computer as normal
