I am unable to program my Virtex-5 TXT device successfully using a bitstream generated with 10.1
This BitGen issue will be fixed in ISE 11.1.
You can also work around this issue in ISE 10.1 by installing the following patch:
To install this patch, extract the zip file to your $XILINX or $MYXILINX folder. This will place the "virtex5.bfd" file into your /virtex5/data directory. After applying the patch, you will need to rerun BitGen on your design NCD.
Note 1: For further information on using MYXILINX, see (Xilinx Answer 2493).
Note 2: This patch also contains the fix for the issue found in (Xilinx Answer 31618).