you two got me thinking..
I chose to hide my SSID before and connect manually but couldn't get it to work.
SSID Broadcast is now on. It Works!
I just need to click my network and type my password. I don't even need to select my encryption, ubuntu already had it right.
I tried turning SSID Broadcast off. DHCP worked, static IP as well but only for a while.
I chose static-ip and removed the "Search Domains" field to force a disconnect. After that I could not get a connection although all options were back to the previous working setup.
It kept asking for the password. Checking the "Show password"-box revealed what seemed like a hex-unicode-kinda phrase to me, no matter what I inserted before.
Turning SSID Broadcast on again got me connected and online in no time.