Somehow directories get set with a read-only attribute that cannot be changed with the GUI.  Use attrib -r to remove the read only attribute.  If a directory where VMware stores snapshots is set to read only, VMware cannot restore snapshots from that directory.  See and  It seems if you customize the folder to get the fancy VMware icon on it, then Windows sets the read only attribute on the folder.  Then at some random time in the future, VMware will not be able to restore a snapshot.