Font problems in 2.3.24

[Cameron Horsburgh]

Hi folks,

I've just downloaded Lilypond 2.3.24 (Debian Sid) from Pedro's 
repository. I had a few font problems, which I fixed by upgrading to the 
latest ec-fonts-mftraced, also from Pedro's site.

Now, however, when I use a global staff size less than 20 points I get 
greater-than signs and other math symbols in the place of note heads, 
and a lot of other notation is similarly affected.

Here's a fairly minimal case score that has the dud behaviour:

%%%%%%%%%%%%%%%%%%%%%%%%%
\version "2.3.22" % this should be 2.3.24
#(set-global-staff-size 18) % the problem happens for all numbers 
less 		than 20

\layout {
        papersize = "a4"
        }
\score {
        {
        \clef treble % No clef appears
        a4 b c' d'
        }
}
%%%%%%%%%%%%%%%%%%%%%%%%%%

Am I doing something wrong, or is this a bug?

(Less important: You may also notice that convert-ly-snapshot didn't 
change the version number correctly -- the original file this is based 
on was 2.2.6, and I'm pretty sure I'm using 2.3.24)

Thanks for your help folks,

Cameron