I was looking through this old question of mine and since what was supposed to be the correct answer up until now, was given by me in the comments, I think I also deserve the credit for it.
The problem lied in the fact that the glyphicon font files downloaded from bootstrap’s customizer tool were not the same with the ones that are downloaded from the redirection found at bootstrap’s homepage. The ones that are working as they should are the ones that can be downloaded from the following link:
http://getbootstrap.com/getting-started/#download
Anyone having problems with old bad customizer files should overwrite the fonts from the link above.