The patch included with this Answer Record fixes this problem for xps_ll_temac_v2_00_a in the EDK 11.1 release.
1. Download the tactical patch from:
http://www.xilinx.com/txpatches/pub/applications/misc/ar32382.zip2. Extract the archive to a temporary folder.
3. Copy the xps_ll_temac_v2_00_a directory from $XILINX_EDK\hw\XilinxProcessorIPLib\pcores\ to the <Project>\pcores folder.
4. Replace the file, <Project>\pcores\xps_ll_temac_v2_00_a\hdl\vhdl\rx_cl_if.vhd, with the file in this archive.
5. Clean the generated files and re-implement the design.
This issue should be fixed in EDK 11.2, which is scheduled to be released in mid-2009.