2. Edit the Simulate Post-Translate/Map/PAR Model process properties, tick "Use Custom Project File" and point to the edited testbench.prj file in the "Custom Project Filename" entry.
3. Run simulation as normal from Project Navigator.
1. Manually edit the testbench.prj file as in Workaround #1.
2. Run simulation from the command line.
fuse -o testbench_isim_par.exe -prj testbench_par.prj testbench
3. Launch the ISIM GUI
Change the package file association to be simulation and re-run the simulation from ISE.