After installing a new VM in VirtualBox Version 4.1.10 I got this error for the first time since working with VirtualBox. I did not do anything with snapshots or config file editing. I just stopped the new installed VM, closed VirtualBox and at the next startup I got this error regarding my only VM in there. After googling a little, this seems to be a known bug in VirtualBox and can be fixed by following comment #29 of this post. After making the recommended changes everything turned out to be smooth again. When the fix will be applied is open til now.