two H.264 video tearing in mplayer on GT520 with -vo vaapi:gl -va vaapi

To technical support center,

I am trying to play two video files of H.264 at the same time on a single screen.
However, playing two video files in mplayer by enabling OpenGL with vaapi mode,
tearing occurs one of two video file during playback.

mplayer -vo vaapi:gl -va vaapi -ao pulse -geometry 1920x1080+0+0 -noborder video1.mp4
mplayer -vo vaapi:gl -va vaapi -ao pulse -geometry 960x540+960+0 -noborder video2.mp4

I suspect a problem with OpenGL double buffer management of device drivers.
A similar problem occur even if the two or more video files.

I send my log file and screen captured file(nvidia-bug-report.log-ghsec.tar.gz)

My PC(ubuntu 10.04LTS) enviroment is as follows.

M/B           : ZOTAC D2700-ITX
CPU           : Intel Atom D2700 2.13GHz
GPU           : Nvidia GeForce GT520
 CUDA Cores      : 48
 VBIOS Version   : 75.19.1b.00.b2
 VRAM            : 512MB
  Graphics Clock  : 270 MHz / 810 MHz
  Memory Clock    : 405 MHz / 897 MHz
  Processor Clock : 540 MHz / 1620 MHz
System Memory : DDR3-1066 2GB
SSD           : OCZ Vertex 4 SATA III 64GB 
OS            : Ubuntu 10.04LTS
Linux kernel  : 2.6.32-44-generic
Nvidia Driver : 304.60 and 304.84
libva         : 0.32.0-1+sds2
libvdpau1     : 0.3-2build1
vdpau-video   : 0.7.3-1
mplayer-vaapi : SVN-r35107-4.4.3

Your prompt response is appreciated.