Run 'ifconfig eth0' assuming that this is your only nic.
If it puts something like that out your config from the OS side is ok.
eth0 Link encap:Ethernet HWaddr 00:13
* inet addr:10.1.1.4 Bcast:10.255.255.255 Mask:255.0.0.0 *
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:366212 errors:0 dropped:0 overruns:0 frame:0
TX packets:206157 errors:0 dropped:0 overruns:0 carrier:0
RX bytes:518728880 (494.6 MiB) TX bytes:16554529 (15.7 MiB)
Interrupt:7 Base address:0x4000
* This is the important part *
I am not sure how this works with sabayon but I wouldn't trust kmenu to setup my nic with gentoo.
Try dhcpcd eth0 and see where that leaves you.