from your screenshot, nameserver is most probably wrong, and default gateway should be smthg like 192.168.1.254, and not 'dsl'; as maro said, use dhcp, so try this:
1. open aterm, and type: sudo killall udhcpc
2. in aterm, type: sudo ifconfig eth0 up
3. in aterm, type: sudo ifconfig eth0 essid YOURESSID key YOURKEY
4. in aterm type: sudo udhcpc -H box -b -i eth0
5. control that you are connected in aterm, type: sudo ping
www.google.de (stop the output with ctrl+c)
Note: YOURESSID is the name of your network; you must write something here;
Note: YOURKEY is the name of your encrypted key (wep or wap key); if you don't have one, replace YOURKEY with "off" (without quotes).