Cause; The issue occurs because the netvault webui page on customer environment is displayed in compatibility view. The setting "Document mode: 7 (Standard)" confirm this.
1. Please switch Document mode to 9 (for IE9), Standard (for IE10) or Edge (for IE11) - after this the netvault webui page should be displayed correctly, if after restart of the browser the issue still occurs please see points 2 and 3.
2. Please make sure whether the netvault webui page has not been added to a compatibility view list and if so please REMOVE them from the list (please visit following site to check how to do that http://www.sevenforums.com/tutorials/1196-internet-explorer-compatibility-view-turn-off.html - OPTION THREE, points 1,2,3,5)
3. By default the compatibility view is turn off for "Trusted sites" zone (Tools -> Internet Options -> Security tab) and if problem still occurs please try to add the netvault webui page to this zone.
Bug number 27509 - I've added a comment when this particular issue occurs.