While running through this howto, I noticed two things that needed rectification in Ubuntu Edgy (6.10)

Firstly, you will need to uncomment the PostgreSQL module in /etc/proftpd/modules.conf when using MySQL. There is some silent conflict there that immediately disconnects users without even attempting to connect to MySQL when the PostgreSQL module is loaded alongside the PostgreSQL module.

Secondly,  there is the following warning:

 "SQLAuthenticate: use of * in SQLAuthenticate has been deprecated.  Use AuthOrder for setting authoritativeness"

 To rectify this, simply comment out that line, and add a line like the following:

AuthOrder mod_sql.c

Which will only allow logins for users in the MySQL database. See this link on AuthOrder for more information:

http://www.proftpd.org/docs/directives/linked/config_ref_AuthOrder.html

Great HowTO, by the way :)