I have had a couple of users complain that they are seeing an issue where the Network tab turns red but none of the fields are red and all are properly filled in.

I was able to duplicate this once by giving my vm a name, selecting the Organization/Location/Compute Resource, going over to the VM tab and selecting the disk/interface/other settings, then going back to the Host tab and selecting a Hostgroup to populate everything else and clicking submit as soon as possible.

The error in the logs when this happens is, "Failed to save: Mac can't be blank, Mac is invalid". Most of the time it seems a blank ip address stops you from provisioning (which takes longer than everything else to populate) and can be resolved by reselecting the domain and subnet, but at least sometimes it's getting stuck where no error is displayed and there is no apparent way to resolve the issue.

I admit that this is kind of a disjointed work flow, but I see this error in our logs 12 times from today (each time clicking submit will cause the same error once you hit the issue, so it is fully possible this has not actually happened 12 separate times, but probably more than once or twice) so for what ever reason it seems reasonable/possible for people to hit it. There might be another way to expose it which I haven't come across as well.