1. Check the power VCC
2. Make sure chip is not over heat
3. Check the jumper settings on the board
4. Scope the JTAG pins
5. Check your setting for the parralel port
6. if there is another xilinx devoce avalible try to program it
I don't think you need to change the bdsl file. I had this problem quite often and mines is usually due to the JTAG cable. I usually power cycle the board and ensure the cable is firmly attached.
This is a list of problems that I have experienced with programming the FPGA and how I resolved it.
I recall some of our parallel 4 cable did not work properly and that was due to a loose connection inside the cable which require resoldering. Other times is due to the flyleads not making contact with the board, and another time restarting Impact helps. Another problem was the PROM not blank and that sometimes cause problem when reprogramming the FPGA.
another problem is the JTAG chain is not properly connected in the board possibly a cracked via.