I'm not sure where the error message comes from---it's not from magic. Apparently inserted from a script? So I don't know how relevant it is. It is possible that there are illegal type overlaps in the I/O cells, but I don't think so. If not, then an abstract view of one or more cells has been read in, which is all covered in obstruction layers as defined in a LEF macro. These obstructions tend to cover the whole chip, so it is possible to route something through an empty area of a cell that happens to be covered in obstruction in the abstract view, which would result in that kind of error. But abstract views can't be extracted (at least not correctly).