Chordmode breaks in 2.10 and 2.11

[Brett Duncan]

In making some changes to a file I had created with LP 2.8, it 
unexpectedly broke under 2.10.14.
I eventually isolated the problem to chordmode. I've since downloaded 
2.11.18 for Intel Mac (I'm running OS X 10.4.8 on a MacBook Pro), but 
the problem remains.

Here's a small example of what doesn't work:

%%%%%%%%%%%%
\version "2.11.18"

\header { title = "Broken chords" }

\score {
   <<
       \new ChordNames { \chordmode { f2 g2 } }
       \relative c' { c2 d2 }
   >>
\layout{}
}

%%%%%%%%%%%%

and here's the error messages:

Parsing...
Interpreting music... [2]
Preprocessing graphical objects...
Layout output to `harmon.ps'...
Converting to `harmon.pdf'...
`gs -q  -dSAFER  -dDEVICEWIDTHPOINTS=595.28 -dDEVICEHEIGHTPOINTS=841.89  
-dCompatibilityLevel=1.4  -dNOPAUSE -dBATCH -r1200  -sDEVICE=pdfwrite 
-sOutputFile="harmon.pdf" -c .setpdfwrite -f "harmon.ps"' failed (256)
programming error: Parsed object should be dead: static 
scm_unused_struct* Prob::mark_smob(scm_unused_struct*)
continuing, cross fingers
programming error: Parsed object should be dead: static 
scm_unused_struct* Context_def::mark_smob(scm_unused_struct*)
continuing, cross fingers
programming error: Parsed object should be dead: static 
scm_unused_struct* Lily_lexer::mark_smob(scm_unused_struct*)
continuing, cross fingers
programming error: Parsed object should be dead: static 
scm_unused_struct* Grob::mark_smob(scm_unused_struct*)
continuing, cross fingers
error: failed files: "/Users/bduncan/Documents/newLilyPond/harmon.ly"

I went into Terminal and ran LP with --verbose. This appears amongst the 
output, just after "Converting to `harmon.pdf":

Error: /invalidfont in --glyphshow--
Operand stack:
  1.4682   0.0   22.9264   -18.7762
Execution stack:
  %interp_exit   .runexec2   --nostringval--   --nostringval--   
--nostringval--   2   %stopped_push   --nostringval--   
--nostringval--   --nostringval--   false   1   %stopped_push   1765   
1   3   %oparray_pop   1764   1   3   %oparray_pop   1760   1   3   
%oparray_pop   1643   1   3   %oparray_pop   --nostringval--   
%errorexec_pop   .runexec2   --nostringval--   --nostringval--   
--nostringval--   2   %stopped_push   --nostringval--   0   
--nostringval--   %repeat_continue   --nostringval--
Dictionary stack:
  --dict:1083/1123(ro)(G)--   --dict:0/20(G)--   --dict:102/200(L)--
Current allocation mode is local
Last OS error: 2
Current file position is 596594
GPL Ghostscript SVN PRE-RELEASE 8.56: Unrecoverable error, exit code 1

The output is a blank staff.