Where is your iTunes library located? Is it on an external HD?
First thing I'd do is Boot into the Recovery volume (boot with the Command + R keys held down), select Disk Utility and repair both the disk permissions and the disk. Reboot normally and see if there's any change.
Next, if needed, delete the following preference files from your Users/Home/Library/Preferences folder:
com.apple.iApps.plist
com.apple.iPhoto.plist
Reboot and open iTunes and then iPhoto and try again.
NOTE: In Lion and Mountain Lion the Home/Library folder is now invisible. To make it permanently visible enter the following in the Terminal application window: chflags nohidden ~/Library and press the Return key - 10.7: Un-hide the User Library folder. This method also works for Mavericks and Yosemite.
For Mavericks and Yosemite go to your Home folder and use the View ➙ Show View Options menu to bring up this window: