When using FTGL texture fonts, everything works perfectly until I use another texture somewhere else in my program. Then the original texture of the font seems to be lost, and as a consequence, the characters are drawn as black dots. After playing with the various parameters of glTexEnvf, I think the problem is simply that the font doesn't load its default texture back when writing.
Is there a way to access this default texture and bind it before writing?
Try surrounding your calls to rendering the font with
glPushAttrib(GL_ALL_ATTRIB_BITS);
and
glPopAttrib();
(as rotoglup suggests.)