Playing 3D games on PS3 works fine. But I tried to download a movie clip from the net with 3D. I connected the PC to the receiver... and the tv is connected to the receiver. All is HDMI1.4

I have the Nvidia Gtx560m graphics card. But I can't get the 3D to work 100%. I have to enable 3D manually through the TV menu... 3D -> side by side. But it seems I'm only getting the 3D about 70% correct...

What can be wrong?