It was a fresh install of 8.1 preview and not an upgrade. It seems that whenever I resume from sleep the Realtek Gigabit PCIe onboard NIC wont work at all.
Ping will just give me a general failure. The only fix is to uninstall the NIC and let windows redetect it and it will work again.
This also even happens if I disable the NIC and renable it in network connections. Different drivers seem to make no difference whether the Realtek or MS driver so dunno what I can do to fix that.
Motherboard is GA-Z68X-UD3R-B3 but I can't see any reason why I have the problem on this board but not on an older board with a similar realtek nic. I mean I can live with the problem but it is a little bit annoying to have to reinstall the NIC every day.