If clearing cache for the app doesn't work, try this:
Go to Settings / Application Manager, tap Menu, then tap Reset App preferences.
If that doesn't work, turn the phone off (all the way off, powered down completely), then boot into recovery. Press and hold, at the same time, the Volume Up, Power and Home buttons. Hold them until you see the Samsung logo, then release all three. It should boot to a text menu. (If it doesn't, turn the phone off and try again.) Use the volume buttons to select the option to clear cache, then press the power button. Then select the option to reboot the phone, and press power.