I've upgraded to nvidia-drivers-256.53 and the tearing seems to have gone away or at least gotten much much better. Thank you!
There is a strange problem now with mplayer (version 1.0_rc4_p20100803). When I use -vo vdpau, upon exiting, mplayer changes my twinview metamode! I suspect this is a bug in mplayer and not vdpau. Here is the Metamodes line from my xorg.conf:
Option "MetaModes" "DFP: 1920x1200 +0+0, CRT: 1600x1200 +1920+0; DFP: 1920x1200+0+0, CRT: NULL; DFP: 1280x800+0+0, CRT: 1024x768+1280+0"
When I exit mplayer it forces me into "DFP: 1920x1200+0+0, CRT: NULL;". It tells me it is "Returning to original mode 1920x1200".
Funny thing is that if I mplayer -vo vdpau $FILE in that metamode then it crashes with a segfault:
VO: [vdpau] 1920x1080 => 3840x2160 H.264 VDPAU acceleration [fs] [vm]
MPlayer interrupted by signal 11 in module: decode_video
- MPlayer crashed by bad usage of CPU/FPU/RAM.
PLMK if you want me to create a new thread regarding this issue. For me, I'm planning to just steer clear of mplayer and smplayer and use vlc and xbmc instead.