In Virtex devices, a problem occurs in which the configuration appears to have completed successfully, but the I/Os never go active (or some other part of the startup sequence does not complete).
This problem occurs because the external pull-up resistor on the DONE pin does not pull up the DONE line fast enough when the FPGA releases the DONE pin. This problem can occur with a 4.7K ohm resistor. An appropriate resistor value for the DONE pull-up is 330 ohm. Usually, you can solve this problem by replacing the 4.7K ohm resistor with a 330 ohm resistor.