Pages disappearing from dashboard

Hi there,

Since updating to the latest release of wordpress I have a problem that occurs when I log into my dashboard.

This is that pages disappear and there is no way to find or edit them.

If I view my site while logged on they are also missing but as soon as I log out the site works as it should.

I need to do some updates and am worried about the stability of my site, any thoughts what might be causing this?