The timing report contains a setup error, but there are no paths listed under the constraint. This occur with paths that have both a hold error and a setup error. When the fast path switch is enabled, these paths appear twice in a verbose report as hold violations, but not as setup violations.
This problem has been fixed in the latest 10.1 Service Pack available at:
http://www.xilinx.com/support/download/index.htm
The first service pack containing the fix is 10.1 Service Pack 1.