Recently, seahorse decided to refuse to operate when GNOME 2.22 was merged in. This was due to FreeBSD lacking unprivileged access to mlock(2) and munlock(2). I've got some patches up on a section discussing this: mlock-support. There are patches to fix Seahorse so that it doesn't crash just because there is no mlock(2) support (bad behavior), as well as a kernel patch to make unprivileged access available on your machine.
Discussion