[Update July 13, 2013 - I was able to deploy the newly issued KB2855336 to all of my physical and guest cluster nodes. There have been no issues so far. The same KB will also show up in most of your VMs as it is a collection of 21 updates touching all kinds of bugs including four stop errors]
[Update July 13, 2012 – For a thank you to Microsoft testers, may I kindly refer to Aidan Finn’s very direct blog called “Something Has Gone Very Wrong With Microsoft Patch Testing”]
[Update July 12, 2013 - Meanwhile Microsoft has expired KB2855336. In WSUS you can no longer approve installation of this update and you are recommended to decline this update
Problem has been acknowledged and KB2855336 has been reissued ]
Unfortunately we again see a problem with Hyper-V clusters just after installing the Windows Updates. The previous one only broke Cluster Failover Manager which could be solved by uninstalling the responsible update or install the fix which came out very quickly afterwards.
This time we face a much more serious problem and should be a strong warning for those responsible for testing updates at Microsoft.
After updating the cluster nodes with the Windows Server 2012 update rollup (July 2013) and when Windows Server 2012 NIC teaming is used with VLANs (not entirely uncommon), you may get a 0x000000d1 bug check on one or more of your cluster nodes. If you analyze the debug, it points to MsLbfoProvider.sys which is for NIC teaming. The upgraded version of MsLbfoProvider.sys is 6.2.9200.16628.
Uninstalling KB2855336 will return you to 6.2.9200.16451 of MsLbfoProvider.sys
Please avoid the July rollup until we find out which part of the rollup is responsible for this problem.
[See updated info top of blog!]