picking problem

I am making a pick function, and it worked fine on Linux, but when I moved it under windows it does not seemd to work. When I try to make hit, it doesn’t work out. When I trace it hits = 0; next time I click on the object I got hits = -1. Can someone help me?
Thanks in advance!

Render what you are trying to pick to screen so that you can debug.

If your drivers are broken, then use another method such as ray poly intersection test.