"You're using Hyper-V and a Failover Cluster and your Virtual Machines share the same Clustered LUN to hold VHD for the VMs. You're also using System Center Virtual Machine Manager 2008 R2 to manage your environment. If you delete a VM that resides on a LUN which's shared with another VM, the other VM may fail," informs Microsoft.
Resolution: "This's by design. SCVMM wasn't designed to allow management of this shared configuration. Sharing a LUN across multiple VMs is an unsupported configuration and may lead to undesirable effects. This problem doesn't occur if you're using Clustered Shared Volumes (CSV). This issue only affects SCVMM 2008 R2," explained Microsoft in KB2423004.