When doing some export and imports of the VM using Hyper-V I found an issue related to security. When System Centre VMM is used in the environment, a security ID is placed on all VM. This security ID stops you from importing the VM into Hyper-V.
When importing via the GUI you get the following message;
While doing some testing I found the following section inside the virtual machine configuration file.
<security>
<sd type=”string”>O:S-1-0-0D:(OA;;CC;5cf72d6e-61d5-4fbe-a05c-1e3c28d742fa;;S-1-5-21-4026737508-1815974660-2349268802-1111)(OA;;CC;5cf72d6e-61d5-4fbe-a05c-1e3c28d742fa;;S-1-5-21-4026737508-1815974660-2349268802-1109)(OA;;CC;5cf72d6e-61d5-4fbe-a05c-1e3c28d742fa;;S-1-5-21-4026737508-1815974660-2349268802-1107)(OA;;CC;5cf72d6e-61d5-4fbe-a05c-1e3c28d742fa;;S-1-5-21-4026737508-1815974660-2349268802-1110)(OA;;CC;5cf72d6e-61d5-4fbe-a05c-1e3c28d742fa;;S-1-5-21-4026737508-1815974660-2349268802-1105)(OA;;CC;5cf72d6e-61d5-4fbe-a05c-1e3c28d742fa;;DA)(OA;;CC;5cf72d6e-61d5-4fbe-a05c-1e3c28d742fa;;S-1-5-21-4026737508-1815974660-2349268802-1104)(OA;;CC;5cf72d6e-61d5-4fbe-a05c-1e3c28d742fa;;S-1-5-21-4026737508-1815974660-2349268802-500)</sd>
</security>
The quick fix is to remove this security element from the xml configuration file.
I have also found that this happens when you remove a Hyper-V from a domain or VMM structure without first removing the virtual. In this case Hyper-V will report no Virtual Machines found on the Hyper-V server. To correct this, remove the security from the configuration files and refresh Hyper-V manager. The virtual machines will all appear again.
Craig Wilson 
Awesome, this did the trick for us
im having this problem.. but in my case the xml configuration file does not contain the security tag.
what can i do..?
It is normally the permissions on the files or the security tag. If the tag is not there then I would be checking the permissions on the files. Just reset the NTFS permissions on the folder structure so Hyper-V can access them.