Hairy lilypond compile problem

[csj <csj@mindgate.net>]

Using a brute-force dpkg-buildpackage -b -rfakeroot on the lilypond
source package results in a build failure. The last three lines of
stdout show:

bison -d parser.yy
mv parser.yy.tab.h out/parser.hh
make[2]: Leaving directory `/xa/build/debian/lilypond-1.4.9/lily'
make[1]: Leaving directory `/xa/build/debian/lilypond-1.4.9'

My attempt at diagnostics is crude at best. From the little I learned
from the man page of the command in question, I was able to produce the
following not too helpful error output:

gamma:/builder/lilypond-1.4.9$ cd lily
gamma:/builder/lilypond-1.4.9/lily$ bison -d parser.yy -v parser.yy
contains 2 shift/reduce conflicts.

Are there any bison gurus out there. Or is this a mere symptom of an
altogether different problem?