Unlike the G750, G75, and G55 series notebooks, the G46VW supports nVIdia 'Optimus' and comes with 2 graphic chips enabled as mentioned at the ASUS website
http://www.asus.com/Notebooks_Ultrabooks/G46VW/#overview"Dedicated NVIDIA® GPU plus Optimus™: more graphics power, longer battery life
NVIDIA® GeForce® GTX 660M GPUs with 2GB GDDR5 video memory allow the latest games to run in smooth high detail for uncompromising experiences. For better efficiency, NVIDIA® Optimus™ technology intelligently switches between integrated and discrete graphics based on application to save power and prolong battery life, so you can go further between recharges."
You may want to check your device manager and tell us which driver versions you have installed for each.
Check the nVIdia graphics settings as well, but hopefully we can get more ideas from other G46VW owners if there are still problems.