[Zope] form validation

[Ian McMeans]

I've got a problem with form validation - I've added some fields to a form
(the form is in a zpt), and the fields work okay. I copied and pasted the
error handling code for the new fields from the pre-existing fields, and
changed the variable names where neccesary. This is on plone's join_form.pt,
by the way.

It works perfectly when input is valid, but when the username field's input
is invalid it doesn't notify the user - the field normally has a box around
it and a text message to the user. On pressing the 'register' button, the
form page is reloaded like it should be, but it doesn't highlight the
username field UNLESS (and this is the odd part) there are also other fields
that are invalid.

I didn't make any changes to the username stuff, so I've got no clue what's
happening. Can anyone make heads or tails of this? Why would the existance
of errors in other fields affect the username field?