Some issues have been seen with the default value of BUFFER_CONFIG_LANEx and an incorrect synchronization of RXBUFRESET between theTXUSRCLK and RXUSRCLK domains. For more details on these issues, please check (Xilinx Answer 43591). To resolve these issues, you must replace the generated GTH wrapper files with the latest wrapper files provided by Virtex-6 FPGA GTH Transceiver Wizard v1.8rev2. To do this, generate the GTH wrapper file in the Virtex-6 FPGA GTH Transceiver Wizard v1.8rev2 in the CORE Generator tool, using the 10GBASE-R Protocol and the component name 'GTWIZARD_10GBASER'.
The Virtex-6 FPGA GTH Transceiver Wizard v1.8 rev2 will be officially released with ISE Design Suite 13.2 Update. In the meantime, a tactical patch is available for v1.8 of the Virtex-6 FPGA GTH Transceiver Wizard. Please check (Xilinx Answer 43591) for instructions on how to download and install the patch.