When using IBM ThinkPad (Laptops), 5.2i and 6.1i iMPACT are unable to find the parallel cable provided with the Xilinx Digilab CoolRunner-II demo board.
This problem is caused by the resistor between pin 8 and 11 of the DB25 connector and ThinkPad's parallel port driving strength.
To work around this issue, simply turn the board around and short pin 8 and 11 or pin 8 and 12 of the DB25 connector (parallel port).
A detailed drawing can be found on the Digilab's user manual.
http://www.digilentinc.com/assets/documents/xc2_RM.pdf Page 4 figure 4.