The green vs. white port icon represents the link state of the physical NICs that are defined as uplinks. Make sure the vmnic of this host is connected in the Network Adapters view or in the uplink port group view.
Also try to refresh the port in the uplink port group view if it says disconnected.
Are all blades inside the same enclosure? Maybe you can isolate it to one particular enclosure one where Virtual Connect module downed the links via SmartLink due to external link failure or something.