I use your lovely plugin a lot and I've never had a problem before. However, I've just set it up on a site and when I try to look at the site I see the down for maintenance page.
I saw on this thread http://wordpress.org/support/topic/when-logged-in-cant-see-pages?replies=3 that this can occur when WordPress is in a subfolder, which it is, but then again I usually install to a subfolder. You imply in your response in that thread that this can occur when the subfolder set up is misconfigured. I don't think mine is, but could you tell me what sort of misconfiguration would cause this?
The site is http://www.chocolicious.co.uk