Having returned to the game after 3 years (give or take) I have to remember a lot of stuff!
The question is regarding attacks of opportunity and the feat Combat Reflexes. The rules clearly state "If you have the Combat Reflexes feat, you can add your Dexterity modifier to the number of attacks of opportunity you can make in a round. This feat does not let you make more than one attack for a given opportunity, but if the same opponent provokes two attacks of opportunity from you, you could make two separate attacks of opportunity (since each one represents a different opportunity)."
So what exactly constitutes a "given opportunity"? Does a character with combat reflexes makes two attacks of opportunity in the same round, against the same opponent who fires two arrows?