Openlayers 2.12 + Firefox 15 = OSM Layer not showing

Question

I know it's due to the new Access-Control-Allow-Origin in OL 2.12, but it is still not functional to me. I've followed instructions on here on stackoverflow.

Firefox version

15.0.1

Apache2 config

In /etc/apache2/sites-enabled/000-default I've set:

<Directory /home/fradeve/public_html/ark-oia/*>            
    Header set Access-Control-Allow-Origin *
</Directory>

OL OSM layer config

var osm_layer = new OpenLayers.Layer.OSM('OSM Layer', null, {
    transitionEffect: 'resize',
    tileOptions: {crossOriginKeyword: null},
    resolutions: [...],
    serverResolutions: [...]
})

But OSM layer is fine on Safari, Chromium 20.0.1132.47, but not in Firefox. What am I missing?