After installing Security Update MS11-072, files opened using a UNC path which are linked to files within the same folder save the link references as absolute references. If you move the location of the folder to another location the link will still reference the original UNC location.
Installing the October CU will resolve the issue introduced in the security update.
This only effects files with the new Excel extensions: xlsx, xlsb, xlsm
links XL2007 update