Assigning more than one virtual CPU
If you are running Citrix XenServer EE 5 Update 2 on a Windows 2008 EE SP1 (x84-64) virtual machine, you can experience the Windows stop message if you configured more than one vCPU.
Multiple Citrix XenServer hosts
If you are running multiple Citrix XenServer hosts as part of a shared resource pool, one of the hosts can become unresponsive when you are completing system actions, such as adding and removing nodes, or resetting nodes.