This is not a real error. The issue occurs because the DRP space is not masked correctly in the bit file; therefore, any change results in the Readback signature changing and flags the error.
This issue has been resolved in ISE Design Suite 14.2. If you are not using the GTH DRP, then you will not experience any problems. If you require further assistance with this issue, please contact Xilinx Technical Support: http://www.xilinx.com/support/clearexpress/websupport.htm