1. Your videocard does not support Realview. Find a certified videocard here: http://www.solidworks.com/sw/support/videocardtesting.html
2. To access Software OpenGL, close all your SolidWorks files first.
Alin is correct - your card is not listed on the real-view capable list.
Is it possible that what you thought you saw earlier was done using Photoview instead of realview?