Currently Being ModeratedFeb 14, 2013 2:16 AM (in response to Sarahc2002)
What Mac do you have, what version of OS X, and what mouse?
Currently Being ModeratedJan 10, 2014 6:25 PM (in response to Klaus1)
I have a Mac book air
Currently Being ModeratedJan 10, 2014 11:27 PM (in response to Blancaone)
Could be many things, we should start with this...
If 10.7.0 or later...
Bootup holding CMD+r, or the Option/alt key to boot from the Restore partition & use Disk Utility from there to Repair the Disk, then Repair Permissions.
Any change on reboot?