It looks like there is a bug in how OpsView displays the server failure notice. The behavior we are seeing is that when the OpsView server is not accessible, the page header goes away, but there is no obvious error message unless we hover over the refresh icon.
Once we hover over the refresh icon, it will show a large on screen error.
Looking at Firebug, it looks like the DIV with ID refresh_error_dialog is incorrectly located within the refresh_status div that is only visible during the hover.
We are using Build: 3.20130903.0.13498 of the community edition of OpsView.