Text edit settings

when I want to change the value or edit text I am unable to edit with back space. Either I remove entire text or, select every time before edit by the following procedure. For example to edit value field, right click mouse for a menu and select input method as ‘simple’ or ‘none’.
Is there a bug, or something wrong with my computer settings, or Ubuntu version. I am using Ubuntu14.04.1, and Kicad version is the latest available.