bug opengl with geforce


I found a bug if someone know how to fix it…

I work on WinNT with GeForce3 / 4, I use 2D OpenGL drawing on a window.

If i move the window and if i draw on a sub part of the backbuffer WITHOUT clear the backbuffer, then the entire BackBuffer is shift left or right (about 10 pixels)
Further more i don’t draw in a main loop, just when its necessary.

Thanks in advance.