ttda on R 2.1.1: error

Hello,

I'm trying to use the package ttda, wich is involved in text analysis,
for my own data about answers in a company survey.
I've installed it, as well as ispell, but when trying to use an 
example:

zz <- file("stupid.txt", "w")  # build a data file
cat("{comment - stupid data file} \n"              , file = zz)
cat("<uci=1> Hush-a-bye, baby,     \n"             , file = zz)
cat("     in the tree top.  \n"                    , file = zz)
cat("<uci=2> When the wind blows, \n"              , file = zz)
cat("     the cradle will rock. \n"                , file = zz)
cat("<uci=3> When the bough breaks, \n"            , file = zz)
cat("     the cradle will fall, \n"                , file = zz)
cat("And down will come baby, \n"                  , file = zz)
cat("     cradle and all.    \n"                   , file = zz)
cat("{Nursery rime} \n"                            , file = zz)
close(zz)
dummy.example <- ttda.get.text(textfile = "stupid.txt")
dummy.example <- ttda.uce(dummy.example)

error in identical(native.enc, MacRoman) :
	native.enc not found

it lamentably fails.

how about this ?
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