I recommend you to download
Onyx. It is a tool that can help you fix problems on your system. Go to the 'Automation' panel, select all the options and click on the 'Execute' button. Then restart your computer and check if your problem has been fixed.
If your problem has not been fixed you will have to run the tasks manually. Note that you will be asked to reboot after each task. There is no need to do that, just reboot once you have run all the tasks.
Maintenance panel
- Run the permissions reparation from the first sub-panel by clicking on 'Execute'.
- Select the 'Daily', 'Weekly' and 'Monthly' scripts from the 'Scripts' sub-panel and click on the 'Execute' button.
- Select 'LaunchServices' and 'dyld's from the 'Rebuild' sub-panel and click on the 'Execute' button. (You can also select to rebuild the Spotlight Index).
Cleaning panel
- Check everything from the 'System' sub-panel and click on the 'Execute' button.
- Check everything from the 'User' sub-panel and click on the 'Execute' button.
- Check 'Browser Cache' and 'Download Cache' from the 'Internet' sub-panel and click on the 'Execute' button.
- Check 'System and Users' from the 'Fonts' sub-panel and click on the 'Execute' button.
- Check everything from the 'Logs' sub-panel *BUT* 'Conversations log of instant messaging' and click on the 'Execute' button.
- Check 'Recent Items', 'Obsolete items' and 'Previous 'iTunes Libraries' from the 'Misc' sub-panel and click on the 'Execute' button.
Let me know if that fixes the problem.