Multiattach disks break snapshotting

[Stephen Thomas]

Steps to reproduce:

1. Move the .VirtualBox and "VirtualBox VMs" folders aside to force VirtualBox to start with fresh ones.
2. Launch the VirtualBox GUI.
3. Click New to create a new VM.
4. At "Welcome to the New Virtual Machine Wizard!", click Next.
5. At "VM Name and OS Type", type master into the Name box and click Next.
6. At "Memory", click Next.
7. At "Virtual Hard Disk", click Next.
8. At "Welcome to the Create New Virtual Disk Wizard!", click Next.
9. At "Hard Disk Storage Type", click Next.
10. At "Virtual Disk Location and Size", click Next.
11. At "Summary", click Finish to dismiss the Virtual Disk Wizard.
12. At "Summary", click Finish to dismiss the Virtual Machine Wizard.

The GUI should now be showing you a new Windows XP VM called "master".

13. Choose File->Virtual Media Manager.
14. Click "master.vdi", then click Release, click Release to confirm, then click OK to dismiss the Virtual Media Manager.
15. In a Terminal window, type

    vboxmanage modifyhd VirtualBox\ VMs/master/master.vdi --type multiattach
    

16. Back in the GUI, click New.
17. At "Welcome to the New Virtual Machine Wizard!", click Next.
18. At "VM Name and OS Type", type slave into the Name box and click Next.
19. At "Memory", click Next.
20. At "Virtual Hard Disk", click "Use existing hard disk", then click Next.
21. At "Summary", verify that the Boot Hard Disk is "master.vdi (Multi-attach, 10.00 GB)" and click Finish.

The GUI should now be showing you two Windows XP VMs, "master" and "slave".

22. Close the GUI, wait 15 seconds and open it again.
23. Click "slave", then click Snapshots.
24. Click the camera button to take a snapshot.
25. At "Take Snapshot of Virtual Machine", click OK.
26. Close the GUI, wait 15 seconds and open it again.

This procedure doesn't involve running a VM, so no log files are generated.

Expected result:

"Slave" should remain accessible and should have one snapshot titled "Snapshot 1".

Actual result:

GUI shows "slave" as "Inaccessible".