Hmm... yeah, mine are disconnecting constantly. They stay connected for about 1 minute and then disconnect. It makes it hard to vmotion. We're going to have shut down all the customer VM's to be able to reboot. 
And I think its storage, because the clusters share datastores, except for a few hosts that use a different set of datastores, and those one's stay connected. This is affecting Dell on 4.1, and HP and Cisco UCS on 5.1. The one's staying connected are on the same UCS fabric too as the others, just are not mapped to the common datastores.