Else please try this option:
type about:config in address bar.
And search for entry "general.useragent.locale" and change to ta-IN there.
Then close firefox and open again.
In Mandrake 10.1 OS I tried this pack, I already had few GPLed Unicode
tamil fonts.
I am not sure if the problem is because of non availability of
tamil(unicode) fonts in the OS. Need to investigate.