See this discussion which may or may not be related: how to troubleshoot: all physical network interfaces stop responding
In summary, sometimes I have to do a hard reboot of my physical machine because the NICs stop responding. This problem has been ongoing for at least a year, but usually after a reboot everything would just come back up with no problem.
In the past month or two, a new problem has presented itself which is that one VM seems to get stuck at the "starting" phase. I have 6 VMs on this box, and all are set to auto-start at boot, with a staggered 2 minute start. After this problem started, I tried increasing to a 3 minute staggered start, but it made no difference.
The tasks pane shows the server stuck at 0% on starting, and any attempt to cancel just locks up the Vsphere interface. I end up having to hard reboot the machine again, and after a second hard boot, the VM comes up with no problem.
Any idea what could be causing this? Not sure if it is important, but the VM is a Windows 2012 R2 box running Microsoft Exchange. The VM has 24GB of RAM available to it, out of a total of 96GB on the box, and only about 50GB allocated.