FNAME must be provided - Please enter a value

Hi there,
I have integrated JoomlaMailer within a Joomla website. I've added the module to appear in the footer of the website so that a user only needs to enter their email address to sign up for the newsletter. In the Module Manager for the MailChimp Signup, I've selected only the Email address for the fields. However, when I try and test a sign up, I enter an email address and then get the following error:

FNAME must be provided - Please enter a value
Try again

Can someone tell me how I configure it so that they only need to enter an email address to sign up or point me in the right direction to solving this problem.

Many thanks, Martin

joomlamailer version: 1.7.2
Joomla! version: 2.5.16
PHP version:
MySQL version:

Can anyone help? This is quite urgent.

I would like to know that too...

I have searched all language strings and in the sourcecode of every file, but no luck!