In a Virtex-5 device, if a x16 or x32 configuration interface is used in conjunction with BitGen compression 9.1.01, the Multiple Frame Write command is not handled correctly.
This problem has been fixed in the latest 9.1i Service Pack available at:
The first service pack containing the fix is 9.1i Service Pack 2.
This problem is the length of the Multiple Frame Write command that is sent to the device. In 9.1.02 and later, the proper command length is applied to the device to allow compression to run as expected.