window not responding and 'graying out'

LO writer stops responding and the screen becomes gray (the text still shows) when I do such things as inserting a document into another document or any large data movement. My system seems to be adequate (AMD Phenom II x3, 650 W power supply, 7.8 gb memory, good quality but older video card) and the Ubuntu OS is 16.04 and a clean install. Are the symptoms attributable to the OS or is the likely problem the video card? Comments appreciated.