Just out of curiosity I tried as non-root and worked perfect..... solution do not do as root...duh..I leave this just incase I forget.
BozMac-3:~ root# /usr/bin/VBoxManage modifyhd /Users/gboswell/Library/VirtualBox/HardDisks/Windows\ 7\ NewHardDisk1.vdi -type immutable
Oracle VM VirtualBox Command Line Management Interface Version 3.2.10
(C) 2005-2010 Oracle Corporation
All rights reserved.
ERROR: Could not find a hard disk with location '/Users/gboswell/Library/VirtualBox/HardDisks/Windows 7 NewHardDisk1.vdi' in the media registry ('/var/root/Library/VirtualBox/VirtualBox.xml')
Details: code VBOX_E_OBJECT_NOT_FOUND (0x80bb0001), component VirtualBox, interface IVirtualBox, callee nsISupports
Context: "FindHardDisk(Bstr(FilenameOrUuid), hardDisk.asOutParam())" at line 430 of file VBoxManageDisk.cpp