I did set it to 75hz, my friend was trying to run it on his mom's computer...guessing she had an older one, didnt get the specs
If it's a Mac, there may be another issue: some of the older ones don't support full-screen OpenGL applications at all, and will only run them in windowed mode.
Which does bring up the point: We can programmatically obtain the list of supported resolutions and refreshrates -- but is it possible to find out whether or not a computer supports full screen OpenGL or not?