Error on Windows build: "unable to re-encode"

Dear developers,

while our package TripleR (hosted on R-Forge) builds well on Mac and Linux, the Windows build shows following error (http://r-forge.r-project.org/R/?group_id=418&log=build_win32&pkg=TripleR&flavor=patched):

Fri Feb 26 00:53:38 2010: Building binary for package TripleR (SVN revision NA)
using R version 2.10.1 Patched (2010-02-24 r51172) ...

* installing to library 'R:/R/lib/CRAN/2.10'
* installing *source* package 'TripleR' ...

  Using auto-selected zip option '--use-zip-data'

** R
Error : unable to re-encode 'RR.r'



I found the piece of code producing the error in the function .install_package_code_files in the file src/library/tools/R/admin.R:
    ## assume that if locale is 'C' we can used 8-bit encodings unchanged.
    if(need_enc && !(Sys.getlocale("LC_CTYPE") %in% c("C", "POSIX"))) {
        con <- file(outFile, "a")
        on.exit(close(con))  # Windows does not like files left open
        for(f in codeFiles) {
            tmp <- iconv(readLines(f, warn = FALSE), from = enc, to = "")
            if(any(is.na(tmp)))
               stop(gettextf("unable to re-encode '%s'", basename(f)),
                    domain = NA, call. = FALSE)


However, I don't really know what that means.
I already tried to encode the source file both in UTF-8 and in latin-1, but neither worked.


Did anyone encounter the same problem / any suggestion?