If you're absolutely sure that they're not in the incorrect place, then the most common cause I come across for problems like this when it comes to serving web-fonts is that the server isn't configured to serve the correct mime-type for the files.
According to HTML5 boilerplate these are the mime-types that you should be using when serving web fonts:
woff: application/font-woff
eot: application/vnd.ms-fontobject
ttf & ttc: application/x-font-ttf
otf: font/opentype