The current version of GPGMail will NOT work in Snow Leopard.

Happily, a developer has volunteered to bring it up to compatibility with Apple Mail v4 (the version shipped with Snow Leopard) if Mail is set to 32-Bit mode via Get Info. This is not a perfect solution, but it will work.

The problem apparently is that the code for GPGMail is too old to work in 64-Bit mode. GPGMail will require a significant rewrite to work as 64-Bit, and there is no schedule as yet for the rewrite.

Meanwhile, PGP is also NOT Snow Leopard Ready. But an update for PDP is also in the works.

BTW: Please ignore the newbies who post nonsense about GPG 'not' working in Tiger or Leopard. It actually works perfectly. The problem, as usual, is that these people refuse to RTFM. Therefore, they have no idea how to get GPG to work. This is complicated software compared to most and is therefore not going to be adequately understood by many people. Their inability to use the software does NOT equate to the software not working. So there.