The ISE Simulator is a single language simulator. The output simulation netlist, as well as the intermediate test bench file created for a Test Bench Waveform (TBW) file, will match the language specified by the Generated Simulation Language property. Therefore, the Generated Simulation Language selection in the Project Properties should match the project source type (Verilog or VHDL). Additionally, in 7.1i, if the Generated Simulation Language is changed after a simulation has been attempted, Project Navigator fails to reset the Generated Simulation Language to the new value.
To work around this, do the following:
1. Run Project -> Cleanup Project Files.
2. Close and re-open Project Navigator.
This problem has been fixed in the latest 7.1i Service Pack available at:
http://support.xilinx.com/xlnx/xil_sw_updates_home.jspThe first service pack containing the fix is 7.1i Service Pack 1.