VirtualBox: Error: Cannot register the hard disk

If when cloning VirtualBox VMs you get an error like this: $ VBoxManage clonehd WinXP-IE7.vdi WinXP-IE8.vdi VirtualBox Command Line Management Interface Version 2.2.4 (C) 2005-2009 Sun Microsystems, Inc. All rights reserved. ERROR: Cannot register the hard disk '/home/scol/.VirtualBox/VDI/WinXP-IE7.vdi' with UUID {3858b1b1-c306-4505-8264-235af812f337}…

Running VMware images under VirtualBox

I use the excellent VirtualBox on Ubuntu but I had a specific Debian dev environment VM that I'd previously run under VMware Fusion on my work mac when it used to have OSX on it ;-). The current versions of VirtualBox (2.2.4 in my case) support running vmdk…