modelsim altera 10.1 nativelinke error

Each time i try and run modelsim from tools->run simulation tool->rtl simulation i get a nativelink error.

Error: Cant launch the modelsim-altera software -- the path to the location of the executable for the modelsim-altera software were not specified or the executable were not found at the specified path.

if i go to tools->options->eda tool options under modelsim-altera the correct file path is there "c:\altera\13.1\modelsim_ase\win32aloem\" and if i got into that folder the modelsim.exe is there and i can launch the program from that exe.

Under assignments->settings->eda tool settings->simulation the tool name selected is modelsim-altera.

any help fixing this error would be greatly appreciated thanks.