This came in three weeks ago from the fine folks at Assault on 13th Labour, a movement dedicated to solving Perplex City card #251 :

Perplex City, an Alternate Reality Game based around puzzle cards and storytelling, features one card that has yet to be cracked: an RC-64 encrypted plaintext. We’ve created a distributed client and are looking for people with spare cycles to lend a hand. The program requires .NET or Mono (it works on Linux and OS X, as well as XP). Prizes are on offer for the first solve!

Word on the street is that this looks to be as tough a puzzle as the Alternate Reality Gaming community has come across, and hopefully, with a few more volunteers, the card can finally be solved. Perhaps a little history will be made along the way.