I'm assuming that as you've said you can edit some, the problem doesn't start until you actually open the settings (i.e. there isn't a padlock showing on the setting icon stopping you from even getting in).
If there are small squares sitting beside the 'greyed out' settings, trying clicking that first so it lights up green, this essentially unlocks the setting. You can lock it back down again by clicking the square to 'turn it off'. Not really sure why you have to unlock individual settings, always seems like a pointless step to me!