This reply may help you:

www.artio.net/support-forums/joomsef-fre...s-and-joomsef-3#9151

Hi,

I had the same problem recently and initially thought it was an Artio JoomSEF issue.

With Artio JoomSEF turned on, and handling SEF for the Contacts component, when submitting the contact form it would throw a "500" error page.

After some investigating, I noticed that the template override for com_contact was missing a hidden field for "option".

Check your template override for com_contact, e.g.

/templates/YOUR_TEMPLATE_FOLDER/html/com_contact/views/contact/tmpl/default_form.php

<input type="hidden" name="option" value="com_contact" />
<input type="hidden" name="view" value="contact" />
<input type="hidden" name="id" value="<?php echo $this->contact->id; ?>" />
<input type="hidden" name="task" value="submit" />
<?php echo JHTML::_( 'form.token' ); ?>

Make sure it has the <input type="hidden" name="option" value="com_contact" /> field.

Worked for me.

Thanks.