This error might be caused by the existence of 'COMP' property in the EDIF netlist. The COMP property conflicts with an obsolete XILINX pack constraint that is still converted to BLKNM constraints. Beginning with ISE 13.2, the COMP properties will be ignored by the ISE implementation tools. Meanwhile, the problem can be avoided by removing the properties from the EDIF file using a text editor.
(property COMP (integer 0))
(property COMP (integer 1))
(property COMP (integer 2))