1. go into the VMM database to the table tbl_WLC_VObject, and change the ObjectState field of the problem VM, which probably has the value 104, to value 1

** At this point, i went direct to the table and edit the value manually. Of course I did this because this I a Lab environment.

update dbo.tbl_WLC_VObject
set ObjectState = 1
where Name = '<VM name>'

2. in VMM admin console, you're VM will now have the status missing, now just delete the VM and it's gone.

Answer found here on :  --> http://social.technet.microsoft.com/Forums/en-US/virtualmachinemanager/thread/872034ba-3545-4431-b9f6-07ee8c65188b