Just noticed this message...

The issue is your glOrtho setting. Since your viewpoint is at 0/0/0, part of the line is behind you. Try using glOrtho(0.f, 1.f, 0.f, 1.f, -1.f, 0.f);

Note - this is a Perl forum, and your example is in C - a better to way to reach me is via my POGL site.

You can also find great tutorials at NeHe

Good luck!