Invite Anyone page has no theme

I’ve added the Invite Anyone widget to a side bar, and I can enter an email address and press Continue.
The next page that appears is http://mydomain.com/members/me/invite-anyone which has the options for sending the invite, but it doesn’t bring in the site theme. Viewing source only shows the divs for the page itself, no html, head tags etc.
It does actually work and send the email out, but obviously looks very wrong.
Any ideas how to fix?

http://wordpress.org/extend/plugins/invite-anyone/