AVAVT: I think is the solution here. The best Black can do is a seki in gote by playing a:
Herman: My instincts are screaming at me that must be the solution :-D
Dave: Maybe I am blind but I do not see how White follows up here. eliminates one of the key defects in Black's position.
unkx80: I think this should be right.
AVAVT: Hm.. yeah that looks like the solution.
This problem is pretty cool. At the first glance, there're so many defects in Black's shape that you think these stone are so dead already no matter where you play. But when you actually try to kill, it's not that easy :D