Fonts loaded from another site using @font-face do not display

When loading a font using @font-face in CSS, the font displays correctly if the font file is local to the web site. If loading the font from another web site, the font file is loaded (as displayed by firebug and by server logs), but the font is not rendered. I.e. : this works @font-face{ font-family:'HelveticaNeueUltlt'; src:url('/fonts/HelveticaNeueUltlt.eot'); src:url('/fonts/HelveticaNeueUltlt.eot?#iefix') format('embedded-opentype'), url('/fonts/HelveticaNeueUltlt.woff') format('woff'), url('/fonts/HelveticaNeueUltlt.ttf') format('truetype'), url('/fonts/HelveticaNeueUltlt.svg#HelveticaNeueUltlt') format('svg'); font-weight:normal; font-style:normal; } But this doesn't work : @font-face{ font-family:'HelveticaNeueUltlt'; src:url('http://s3.mycompany.com/fonts/HelveticaNeueUltlt.eot'); src:url('http://s3.mycompany.com/fonts/HelveticaNeueUltlt.eot?#iefix') format('embedded-opentype'), url('http://s3.mycompany.com/fonts/HelveticaNeueUltlt.woff') format('woff'), url('http://s3.mycompany.com/fonts/HelveticaNeueUltlt.ttf') format('truetype'), url('http://s3.mycompany.com/fonts/HelveticaNeueUltlt.svg#HelveticaNeueUltlt') format('svg'); font-weight:normal; font-style:normal; }