As of today I would say this challenge is no longer solvable for any of us "normal" users.
So gmaxwell should reconsider the scope or withdraw all but the closest challenges.

This was never ment as a puzzle to solve but a rough estimate what current technology can crack.
We know now that the following challenges are only solvable by big players.
He should spread all remaining funds on the existing solvers (-30 bits) for being grateful on their participation.

The End.