Under Windows 7, when a file is opened in Photoshop CS5 Extended or CS5.5 Extended, a handle is created for the folder. When you close the file, the folder handle isn't removed. So you can't move, rename or remove this folder until you close Photoshop (or use an external process explorer to kill the handle). If there is a long working time between image treatment and file system reworking, you'll lose time to understand why Windows can't modify an unused folder. Never closed folder handles freeze your working tree for the entire imagery session.