I just encountered this problem a few minutes ago, and a quick Google search brought me here.
I am running OSX Lion - 10.7.3
I have my java preferences set to 64 on top.
I downloaded a brand new version of the launcher last night after a saving chunks error and it was working fine.
I booted it up today without an Internet connection (I doubt that's relevant) at first and got the error message. Then tried again after turning the Internet back on again.
I'm totally mystified as to what this might be, but I would appreciate any advice. I've been able to solve all errors with the technic pack from these forums so far, so I know this is the best place.