Corrupted screen image with glx

[fabs0028]

Hello
Well i have some slight problems with the glx extensions to the nvidia drivers.
After some time and mainly when my system turn back from the xscreensaver the display is corrupted and i have to restart X to solve the problem.

I want to precise that it only arrives with the glx extension activated.
It made the same with the 8178,8174 or 7676 drivers.

I run and amd64 ubuntu with a 2.6.14.3 kernel and Xorg 6.8.2.

Here is the the part of the xorg.conf concerning the graphic card :

Section "Device"
        Identifier      "Nvidia Geforce 6600GT"
        Driver          "nvidia"
        BusID           "PCI:1:0:0"
        Option          "RandRRotation"         "on"
        Option          "NvAGP"                 "3"
        Option          "RenderAccel"           "true"
        Option          "AllowGLXWithComposite" "false"
        Option          "NoLogo"
EndSection

I forgot to tell that my card is a 6600gt but you 'd have guessed and the composite extension is disabled.

Here is a screenshot of the problem : screen

Thanx for the help