I had a similar issue, watching videos (or anything network intensive) on either of my VMs would cause the unraid network to disappear (the VMs can ping each other and Tower, but none of them can access the internet), while the rest of the devices (outside of the unraid box) can access the internet and network fine.
I have an Airport Extreme, and turning off ipv6 on the router resolved all my network issues. I guess ipv6 isn't enabled in the unraid kernel, and once the router starts sending ipv6 frames, the unraid server started ignoring them and became nonresponsive network-wise until an ifconfig eth0 down/up.
Hope this helps.
