I've been using VirtualBox on 64 bt Ubuntu 14.04 for some time, and believe that the updates are set to be automatic.

Recently, I went to use one of the virtual machines running my old Windows XP (I miss the Shapeware version of Visio, and there really isn't any Linux software that comes close). I had "Saved" this VM. When I went to "Start" it, the screen showed up just fine during the "Restore" process, but then died when the progress bar reached the end.

The message I received was:

Unsupported version 11 of data unit 'vga' (instance #0, pass
0xffffffff (VERR_SSM_UNSUPPORTED_DATA_UNIT_VERSION).

Asking for more details, I got the following three lines:

Result Code: NS_ERROR_FAILURE (0x80004005)
Component: Console
Interface: IConsole {8ab7c520-2442-4b66-8d74-4ff1e195d2b6}

Apparently I need an updated data unit 'vga' but I don't know whether that's a VirtualBox thing or an Ubuntu thing and, in any case, I have no idea where to find such a thing.

Can anyone tell me how or where to start troubleshooting this?

Many thanks...

One of the web posts suggest to delete the snapshot.

I doubt it has anything to with vga.

I wonder if this is the VB extensions having been updated while XP still has the old drivers. Windows seems to simply die whenever there is a driver problem. Have you tried starting XP in safe mode and installing the latest VBextensions?

I had similar or even the same problem recently (I don't remember the error message exactly). After updating VirtualBox I could not start a VM, which was saved as running. I mean I took a snapshot of a running system and then restored this snapshot instead of booting the system.
I had previous version of VirtualBox available, so I simply started the VM in it and properly shut down the guest system. Then I could boot it with new version of VirtualBox with no problem and take another snapshot of the running system.
If you have the snapshot with saved running system, try deleting the "runtime" information of your snapshot (the .sav file). It would be like hard reset (switching off the power), but will preserve the data written to disk.

I'm on 14.10 (Ubuntu-Gnome) and I had some weird problems with VBox, I keep my vm's on a usb external drive and periodically they would be either be corrupted or simply disappear on closing VBox, this generally happens to saved machines, but machines I shut down at times exhibited the same behavior.
May not be the same issue but I have to wonder what kind of problem it's having with external usb drives.

Thanks to all ...

Deleting the Snapshot indeed solved the problem.

This can easily be done from within VirtualBox with the menu sequence "Machine | Discard Saved State", making sure of course to have the correct vm highlighted.

Thanks for the update and solution.