possible Sweave problem in rdevel build on Debian 6.0.8?

Dear R-Devel,

Note:  I posted a similar message to R-sig-debian yesterday because I
assumed it was a Debian issue, received response that it it may be more
appropriate for r-devel since it involves building from the svn version.

As of Oct 21, we are running into a build failure when trying to
compile the development version of R from the svn repository.  The
problem still persists as of Revision:64096:

We are running:

./configure && make -j4 distclean && ./configure && make -j4

[lots of normal compile output not shown...]

building/updating vignettes for package 'utils' ...
processing 'Sweave.Rnw'
Error: running Sweave on vignette
'/net/home/rpackagebuilder/src/R.trunk/src/library/utils/vignettes/Sweave.Rnw'


failed with message:
<text>:1:1: unexpected '|'
1: |
       ^
Execution halted
make[1]: *** [vignettes-lattice] Error 1
make[1]: Leaving directory
`/net/home/rpackagebuilder/src/R.trunk/src/library'
make: *** [vignettes] Error 2


The same vignette compiles without error on the same machine using the
stable release version of R (which we also build from source with same
commands).

Dirk reported yesterday that he was unable to reproduce the problem on
r-devel svn "..Using Ubuntu 13.04, current"

Does anyone have suggestions on how I might debug this further to
determine if this is an issue with Sweave, or something with our system
configuration which would impact one build and not the other?  When I
diff the files in utils I see quite a few changes to Sweave between the
stable and devel branches, but I'm not sure how to interpret them.

thanks for your help,
    -skye