Not sure if this is a bug or a just an specific use case that went wrong. Anyway, i hope it helps people.
I was having problems embedding fonts using @font-face rules on FF and using CDN77 problems as generic mirror and after a lot of tests, i noticed that the htaccess generated by W3TC on the CDN subdomain was missing the point before the name. It was htaccess instead of .htaccess and this was preventing the FF to read the Header set Access-Control-Allow-Origin "*" directive properly
So, as soon as changed the file name, it worked.
Dreamhost VPS LAMP
W3TC CDN self-hoste domain set, uploading to a specific sub-domain.
( static.jornaldafotografia.com.br )
CDN77's getting the files from this sub-domain and serving to 3 new CNAME sub-domains of mine.
( static1.jornaldafotografia.com.br, static2, static3 )