How to avoid UI freezing when items are being rendered into dom

I see my navigation and other components freeze (not responding to hover/click events) for some seconds.. after model for a particular route has been fetched.. Has encountered something on like this?

Possibly it is because of the DOM being rendered... Any idea how can i avoid that?

Same thing happens, when I load more items and append it to DOM..

I am on ember-cli@0.1.15 with ember version 1.8.1