Finally found a fix!
This seems to be the bit of code that should be running it in administrator/components/com_k2/views/item/tmpl/default.php, around line 720

I have added <?php JHTML::_('behavior.modal'); ?> which has fixed it, but not sure if this is correct PHP and if this then goes on to break anything else?


<?php if($this->mainframe->isAdmin() || ($this->mainframe->isSite() && $this->permissions->get('editAll'))): ?>


<?php JHTML::_('behavior.modal'); ?>

<a class="modal" rel="{handler:'iframe', size: {x: 800, y: 460}}" href="index.php?option=com_k2&amp;view=users&amp;task=element&amp;tmpl=component"><?php echo JText::_('K2_CHANGE'); ?>
</a>

<input type="hidden" name="created_by" value="<?php echo $this->row->created_by; ?>" />

<?php endif; ?>

Confirmation of this fix. I was driving myself nuts trying to change the authors. K2 devs should look at this and fix. Don't wan to have to do this eveytime I install k2.....

Worked for me. Thanks for the fix.