When launching any of the "Floorplan" processes from Project Navigator in ISE, PACE opens for an Automotive Spartan-3A DSP design rather than the integrated Floorplanner.
This issue is resolved in the 10.1 Service Pack 3. To work around the issue, follow these steps:
1. Open the integrated Floorplanner.
2. Load the design or, alternatively, you can change the target part to a non-automotive version of Spartan-3A DSP for floorplanning.
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 3.