Hi moscar,
I have just tested your latest kernel (linux-sun7i 3.4.79-1) on a Cubietruck and got a kernel error message right after plugging the ethernet cable that starts with:
<4>WARNING: at net/sched/sch_generic.c:256 dev_watchdog+0x1b4/0x24c()
<6>NETDEV WATCHDOG: eth0 (sunxi_emac): transmit queue 0 timed out
You can see a full log since the machine was booted at
http://pastebin.com/snZA7QhTI will test your kernel on a Cubieboard 2 as soon as possible.
Edited: can you please point me to the u-boot and spl you are using? I've noticed that the u-boot from ArchLinuxARM-sun7i-latest.tar.gz still shows only 1GB for my Cubietruck.