I have selected File -> Copy Project to create a new version of a project. In the Copy Project dialog, I specify a working directory other than the default project directory. However, when I open the new project and run any PlanAhead process for pin planning or constraints, the following error occurs:
"ERROR: launching PlanAhead failed: can't execute "C:\WINDOWS\system32\cmd.exe": The directory name is invalid."
This error occurs because the Copy Project function is defining the working directory using back slashes. The presence of back slashes breaks downstream code which is expecting the working directory to be normalized.
To work around the problem, copy the project again, but after selecting the working directory, change the back slashes in the path to forward slashes.
This issue is resolved in the ISE Design Suite 11.3 update.
NOTE: The ISE Design Suite 11.3 fix will not repair existing projects with the incorrect Working Directory designation, but it will avoid creating new projects with the issue.