Wifi is working again!
Once I understood that I really really must make sure my wifi works before I arrive to YAPC::NA next week, I searched again. This time I had more luck and found several references to this and this.
In this end this is what I did:
1. sudo modprobe -r iwl3945 2. create a file named iwl3945 in /etc/modprobe.d 3. in that file enter the following entries alias wmaster0 iwl3945 options iwl3945 disable_hw_scan=1 4. sudo modprobe iwl3945 5. sudo ifconfig wlan0 up
That's it. Now my computer started to see the wireless networks around and could connect.