Jan: you can write a boot script to run these commands automatically each time your computer turns on. To do that, follow these instructions:
A blank file will open. Add these lines to it:
sudo gedit /etc/init.d/wifi-fix.sh
Make sure you fill in the information about your hex key and essid, of course.
sudo iwconfig atho essid <your ssid here>
sudo iwconfig ath0 key <your hex key here> restricted
sudo iwpriv ath0 mode 3
sudo iwpriv ath0 authmode 2
sudo dhclient ath0
2. save and close the file
3. run these commands:
This should take care of it. If not, let me know.
sudo chmod +x wifi-fix.sh
sudo update-rc.d defaults