In System Preferences, and CDs &DVDs, I've set the drop-down menu for audio CDs to open iTunes. can anyone tell me why it always reverts to Ignore?

Can anyone help me figure out why the setting in System Preferences and CDs & DVDs will always revert to Ignore when I set the drop-down menu to When you insert a music CD, to Open ITunes? I've tried iTunes Help and it told me exactly what I have been doing. I've even tried downloading iTunes again, to no avail. If anyone has had the same problem, please let me know. I would very much appreciate it.