Go to your User's Library folder. If Lion or higher it's hidden.
**Show Library Folder:
Select the Finder in the Dock. Under Go in the Menu bar > hold down the Option key and you’ll see the Library.
Scroll down to Preferences.
Drag com.apple.LaunchServices.plist to the Desktop.
Log out under the Apple in the Menu bar.
Log in and test.
If the problem does not go away, create a new User in System Preferences or log into the Guest account and see if the problem goes away.
If you still need help, please include what version OS X is installed. Look under Apple in the Menu bar > About this Mac to get version installed.