When performing verify with iMPACT, the following error messages occur:
"'1': Verifying device...
ERROR:iMPACT:396 - Readback to map unsuccessful.
ERROR:iMPACT:395 - The number of difference is -1
'1': Verification terminated.
done."
This problem has been fixed in the latest 6.3i Service Pack available at:
http://support.xilinx.com/xlnx/xil_sw_updates_home.jsp
The first service pack containing the fix is 6.3i Service Pack 2.