I set about trying to fix the registration system once and for all. The following was done...

Dumped SQL structure of existing database and fresh install into files. Compared the two files and fixed any differences in structure in our db.

<br />
changed xoops_users 'name' varchar(60) --> 75<br />
changed xoops_users 'level' default to 1 from 0<br />
deleted xoops_user_profile_field 'field_weight' row<br />
changed xoops_priv_msgs 'touseridreadmsg' --> 'inbox'<br />
changed xoops_priv_msgs 'msgidfromuserid' --> outbox<br />
changed xoops_priv_msgs added 'prune' row<br />
Fixed config table<br />

Removed all modules not in use. Deleted module directories. Upgraded all modules that were not current version: RSVP, Protector, Waiting Contents. Upgraded all modules in module administration to restore config settings and check everything was ok.

Hand edited SQL to add dates to broken users, removed extra rows from sps_user_profile table. Checked registration settings in preference - switched to automatic. Tested registration with a user. Changed 'Displayname' to 'Name' in registration form. Tested registration with and without a Department and with spaces and without spaces in name.

Crossed fingers... said a couple of chants... touched wood.

shaboomed.