To work around this issue, use the older versions of the tools, which can be found at the following:
- PACE -> pace_old
- Timing Analyzer -> timingan_old
- Constraints Editor -> constraints_editor_old
This problem has been fixed in the latest 10.1 Service Pack available at:
http://www.xilinx.com/support/download/index.htmThe first service pack containing the fix is 10.1 Service Pack 3.