I click update on a page – I get sent to posts listing (& page doesn't update

For some reason, when I am trying to edit a site (in maintenance mode) whenever I try and update anything ie a calendar feed, a page, a media file – it automatically takes me to the posts listing page (and not updating the page/feed/file I wanted to update)

Please help – this weird happening is making any use of wordpress completely useless. And yet I am sure there is a very simple solution…

Thanks

Simon