Apparently this resolved the problem. Having the same problem on one of my four Windows 7 installations, I am not aware of locking/unlocking the desktop, nor does Win7 Help give any reference to locking/unlocking desktop. Did you mean locking/unlocking taskbar? I have tried locking /unlocking taskbar, checking & unchecking under right click View 'auto arrange' & 'align to grid', deleted icon cache in AppData/Local, found the hard way that the icon spacing otions from Vista are no longer available.Make sure your desktop isn't locked. Right click and confirm that it isn't.
To set mine up I have it set to sort by none checked and have maintain sorting check
This may be what he is talking about