wifi doesnot startup in mountain lion

After installation of mountain lion, os x 10.8.3, the wifi doesnot start up anymore. Whatever I do I don't get the wifi card working.

In the previous os x software (10.6.8) I did not have any problem.

Pls give me a clou to solve this problem without going back to the previous version.

My computer is a Macbook from end 2008 with an Intel dual core processor, so that will fulfill the 10.8.3 requirements.