Oliver Wyman has long had a good financial services risk management practice which I would assume includes insurance. I have some ex-colleagues there and worked with them a few times – they know their stuff.
Otherwise the big, big consultancy opportunity in risk management in the insurance world is Solvency 2. Most of the advisory firms (EY, Deloitte, etc) have white papers on this, but as it is brand new, actual experience is thin on the ground. KPMG have at least one major risk/solvency 2 project at a major insurer – time will tell on whether they can deliver what they’ve sold.