I'm going to toss my hat in the ring (as suggested by the Clarkmeister "jee-whiz" thread) and say 3-bet this every time with a suspect raise from the cut-off. Unless he's the tightest of tighties, one of the 8/2/6.5 rakeback rocks...

What'd he have? AK? and thought you were FOS? Maybe he thought he could get you to fold a JT, T9 type of hand? He'd have plenty of odds to call the 3-bet and fold the riv...