VirtualBox: Could not get the storage format of the медиум

I am running 5.0.10_Ubuntur104061 on Ubuntu 15.10 x64. My guest OS is Windows 7 x64 with all patches.

Maybe it's relevant: I just added discard="True" to my harddisk. After this, I had running the box for about one hour.

One day later, I bootet the Box, checked out for windows updates, and wanted to shut down the box. Somehow, the guest got unresponsive so I closed it.

After this, I could not boot it anymore. I переместите the .vdi and tried to attach it again, but I cannot attach it.

$ vboxmanage showhdinfo Windows\ 7\ X64.vdi 
VBoxManage: error: Could not get the storage format of the medium '/home/david/VirtualBox VMs/TIA/Work/Windows 7 X64.vdi' (VERR_NOT_SUPPORTED)
VBoxManage: error: Details: code VBOX_E_IPRT_ERROR (0x80bb0005), component MediumWrap, interface IMedium, callee nsISupports
VBoxManage: error: Context: "OpenMedium(Bstr(pszFilenameOrUuid).raw(), enmDevType, enmAccessMode, fForceNewUuidOnOpen, pMedium.asOutParam())" at line 178 of file VBoxManageDisk.cpp

$ VBoxManage internalcommands repairhd -dry-run -format VDI Windows\ 7\ X64.vdi 
VBoxManage: error: VDI: invalid header in 'Windows 7 X64.vdi'
VBoxManage: error: Error code VERR_VD_IMAGE_REPAIR_IMPOSSIBLE at /build/virtualbox-JNluby/virtualbox-5.0.10-dfsg/src/VBox/Storage/VDI.cpp(3102) in function int vdiRepair(const char*, PVDINTERFACE, PVDINTERFACE, uint32