Problem with title fonts

[Daniel Hernandez]

Hello group,
I'm a novice Lilypond user. I'm working with lilypond 2.4.5 in debian.
I intalled lilypond with apt-get. Now I'm compiling some lilypond codes,
for example from the lilypond page and not all works fine. The midi an
the scores are ok, but the font of title is not. I see the output from
the examples and the title is in a Roman font (I think computer modern),
but when I compile the same sources the font that I get is a typewriter
font (but not monospaced). I put the result of the comand
$ lilypond --png petite-ouverture-a-danser.ly
in http://www.dcc.uchile.cl/~dhernand/lilypond/ 
How I can get the font correctly?

Thanks
Daniel Hernnandez