Unable to create new user accounts

Hi.

I've been looking in the Reference guide and Tag reference the last couple
of days for this, but haven't been able to fix this;

In the shop I'm setting up you have to register yourself before you can
submit the order. The user database is a MySQL database called "clients". I
have the following line in my catalog.cfg to define the name of the UserDB:
UserDB default database clients

So, in my new_account.html, I have:
[if session logged_in][bounce href="[area account]"][/if]
[if !scratch new]

[if session failure]
<p><font size="2"><b><font color="red">[data session
failure]</font></b></font>
[data base=session field=failure value=""]
</p>
[/if]

[else]
[set new][/set]
[/else]
[/if]

[set NewAccount]
[userdb function=new_account]
mv_nextpage=account
[else]
mv_nextpage=new_account
[/else]
[/if]
[/set]

<form action="[process-target]" method="post">
<input type="hidden" name="mv_click" value="NewAccount">
<input type="hidden" name="mv_doit" value="return">
<input type="hidden" name="function" value="new_account">
<input type="hidden" name="mv_nextpage" value="ord/basket">

-- snip --
(form fields mv_username, mv_password and mv_confirm is here)
-- snip --

</form>


Then, I enter the username password and a temporary password and submit.
After that, I get the register form back, with the following error message:
Unknown column 'test' in 'where clause'

It seems that Interchange executes a pretty bad SQL statement here, but I
can't find any way to debug them (for example make interchange print every
sql query to the error.log).

Have I done something wrong?
Can anyone give me a hint, or point me to the correct documentation?

Thanks!

--
Trond Arve Nordheim