k. I can see that.
For me it happens when I switch from Icon / Icon Details over to table mode. What's going on is the Firefox is complaining that http://server_a/webGui/javascript/dynamix.js?v=1438559246:5 is taking a long time to run. That is not part of CA. But, when it does take a while to load, it eventually does, and the spinner in the top right (Searching..., and the popup both disappear) At that point, any scripts which CA is running is over, and the rendering has been passed off to your browser.
As far as a bug, you shouldn't be seeing "Searching for [blank]", but the long running script isn't part of CA. What's probably happening is that your browser is choking on trying to render the tables and run that script at the same time. Quick fix, don't hit the button to clear the search term.
Thanks for the info