Bug in glReadPixels/dlDrawPixels

I am using Win NT. I wrote a program that use glReadPixels/dlDrawPixels functions and i am getting strange results. When i am runing the program the images looks disorted a little bit. If i am exiting the program and runs it again, after a few time the image looks good!!
Why it is not consistently?
Under Win 98 it’s not happening.

When you find a bug like this isolate it to it’s most simple form and send it to the manufacturer too see if they’ll fix the drivers. They are usually very appreciative of this kind of feedback. Make sure you’re right though or you can end up with egg on your face and not get taken seriously the next time you cry wolf. You can run it against a software implementation or on another OpenGL implementation to see if you’re right. The fact that it works on NT is a good sign but not a guarantee. Tripple check.

Oops, I meant Windows98, but you guessed that I’m sure.

How can i change the implementation of opengl from hardware to software?