Comment 6 for bug 304496

Thanks. How come you added the linux-meta task again?

I've had a look at your logs, and this looks like a configuration issue rather than a bug. When your computer first boots, Network Manager tries to activate your network connection using DHCP (because this is your system-wide setting, and is also the default). However, this fails (presumably because you don't have a DHCP server on your network?), as indicated by the following entries in your log:

Dec 4 10:20:14 estagiario1 NetworkManager: <info> Activation (eth0) Stage 3 of 5 (IP Configure Start) complete.
Dec 4 10:20:14 estagiario1 dhclient: Internet Systems Consortium DHCP Client V3.1.1
Dec 4 10:20:14 estagiario1 dhclient: Copyright 2004-2008 Internet Systems Consortium.
Dec 4 10:20:14 estagiario1 dhclient: All rights reserved.
Dec 4 10:20:14 estagiario1 dhclient: For info, please visit http://www.isc.org/sw/dhcp/
Dec 4 10:20:14 estagiario1 dhclient:
Dec 4 10:20:14 estagiario1 NetworkManager: <info> DHCP: device eth0 state changed (null) -> preinit
Dec 4 10:20:14 estagiario1 dhclient: Listening on LPF/eth0/00:0c:f1:7f:47:05
Dec 4 10:20:14 estagiario1 dhclient: Sending on LPF/eth0/00:0c:f1:7f:47:05
Dec 4 10:20:14 estagiario1 dhclient: Sending on Socket/fallback
Dec 4 10:20:15 estagiario1 dhclient: DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 4
Dec 4 10:20:15 estagiario1 avahi-daemon[4635]: Registering new address record for fe80::20c:f1ff:fe7f:4705 on eth0.*.
Dec 4 10:20:15 estagiario1 gdmgreeter[5138]: Gtk-WARNING: Incapaz de localizar motor de temas na module_path: "ubuntulooks",
Dec 4 10:20:19 estagiario1 dhclient: DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 4
Dec 4 10:20:23 estagiario1 dhclient: DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 5
Dec 4 10:20:28 estagiario1 dhclient: DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 9
Dec 4 10:20:37 estagiario1 dhclient: DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 17
Dec 4 10:20:54 estagiario1 dhclient: DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 14
Dec 4 10:20:59 estagiario1 NetworkManager: <info> Device 'eth0' DHCP transaction took too long (>45s), stopping it.
Dec 4 10:20:59 estagiario1 NetworkManager: <info> eth0: canceled DHCP transaction, dhcp client pid 5139
Dec 4 10:20:59 estagiario1 NetworkManager: <info> Activation (eth0) Stage 4 of 5 (IP Configure Timeout) scheduled...
Dec 4 10:20:59 estagiario1 NetworkManager: <info> Activation (eth0) Stage 4 of 5 (IP Configure Timeout) started...
Dec 4 10:20:59 estagiario1 NetworkManager: <info> (eth0): device state change: 7 -> 9
Dec 4 10:20:59 estagiario1 NetworkManager: <info> Marking connection 'Auto eth0' invalid.
Dec 4 10:20:59 estagiario1 NetworkManager: <info> Activation (eth0) failed.

When you log in, the network activates because it seems that you have set up a static IP in your users network settings. This setting hasn't been made system-wide, which is why your network doesn't work until you log in

Could you please confirm that this is how you have your network settings configured?