I have the same motherboard and I found out that is working fine with 2.4 bios version.
Could you please state to me which one are you using and try to downgrade to 2.4 or 2.5?
In fact, on 2.6 they upgraded the network driver at the UEFI level.
I'm helping out a friend that bought the same mainboard and running the latest bios.
Thank you.