Unable to Migrate / Start / Shutdown VM (Virtual Machine) Dead Beef 

This is a not so common scenario when you try to destroy domain for a VM using following command 

#/opt/xensource/debug/xenops destroy_domain -domid 140

and then you'll see "VM stuck in dying state" in logs and following in list_domains 

Now to the solution :

Scenario 1: You have multiple VMs running on that server :

In this case you'll have to RDP to all machines and turn them down individually. Then you'll have to reboot your XenServer host to fix the server. This error won't let you shutdown VMs from Xen Center/CLI because XenServer is not able to communicate via XAPI (Xen API).

Scenario 2: You do not have anything running on that server

Reboot your server and the issue is resolved.