Apparently some sort of error developed in one of the numerous mySQL databases supporting this forum. At the least, it was interfering with attempts to register as a new user, but may have had more widespread effects.
As of 3 pm Pacific Time of Wednesday 3 June (2009), it seems to have been fixed (by a mySQL "database repair" operation). If you can read this but still are encountering problems or unexpected behavior from the forum, please email me a.s.a.p. (email@example.com).
Sorry about that (no idea what caused it).