Typically, the default sans-serif font in Ubuntu is Lucinda Sans. In the “60-latin.conf” file, I normally add “Arial” somewhere above “Lucinda Sans”, since the one at the top gets preference. Of course, if you change this file, you should rebuild the libfontconfig file.
The other thing is to first make sure the msttcorefonts got installed ok. They should be somewhere in one of the directories pointed to by “/etc/fonts/fonts.conf”. To make sure linux recognizes the fonts, run:
$ sudo fc-cache -f -vHope this helps.