In System Preferences > Network > WiFi > Advanced, delete all references to your wireless network.
Make sure there is a check mark in the "Remember Networks...." box.
Now join you network again and, with a bit of luck, your MB will remember the network.
my MacBook doesn't login to my wlan-network automatically anymore.
It takes minutes until the list of nearby networks and the message "No known network available" appears, despite the fact that my network is listed. When i click on it, I am connected. How can I reset wlan settings, so that I am connected automatically as it should be?