Hi,
Okay since you got the PS3 to connect, then its an issue with your 360... Most likely you need to set the network connection items by hand,...I am assuming now they are on automatic.
You can use an IP for the 360 like 192.168.0.10 subnet of 255.255.255.0 gateway of 192.168.0.1
DNS primary of 192.168.0.1
DNS secondary of 192.168.1.1
Save and reboot the 360, then retest....
If that doesn't work for the 360...try using the other ethernet cabale you started with, then reboot the 360 and re-test....
If you got online with the PS3, then the 360 should work.
SD1