I have three ESXi 5.1 servers that have the Dell 7.2 VIB bundles installed.
They all three discovered/inventoried fine using WS-Man. They all three show up great in OME1.1.1. After a few days, HOST01 became unknown. I attempted to access it through Server Administrator Managed Remote Node and when I go to log in I get an authentication error (100% credentials are good). I would reboot the host and everything would be good. I would rediscover/inventory and it would no longer show unknown. A few days later, the other two hosts do the exact same thing.
There's definitely something strange going on, maybe it's the 7.2 build?