I upgraded a Windows 2008 Hyper-V server to R2 and one of the virtual machine failed to start with error “Account does not have sufficient priviledge to open attachment “<Virtual machine file>” (0x80070005). (Virtual machine ID <GUID>)”.
Hyper-V could not read the virtual machine files due to ACL issues. Added SYSTEM account, etc does not work as Hyper-V has it’s own Service SID “NT VIRTUAL MACHINE”
To resolve this, try the follow: