Converting a Document Term Matrix into a Matrix with lots of data causes overflow

Let's do some Text Mining

Here I stand with a document term matrix (from the tm Package)

dtm <- TermDocumentMatrix(
     myCorpus,
     control = list(
         weight = weightTfIdf,
         tolower=TRUE,
         removeNumbers = TRUE,
         minWordLength = 2,
         removePunctuation = TRUE,
         stopwords=stopwords("german")
      ))

When I do a

typeof(dtm)

I see that it is a "list" and the structure looks like

Docs
Terms        1 2 ...
  lorem      0 0 ...
  ipsum      0 0 ...
  ...        .......

So I try a

wordMatrix = as.data.frame( t(as.matrix(  dtm )) ) 

That works for 1000 Documents.

But when I try to use 40000 it doesn't anymore.

I get this error:

Fehler in vector(typeof(x$v), nr * nc) : Vektorgröße kann nicht NA sein
Zusätzlich: Warnmeldung:
In nr * nc : NAs durch Ganzzahlüberlauf erzeugt

Error in vector ... : Vector can't be NA Additional: In nr * nc NAs created by integer overflow

So I looked at as.matrix and it turns out that somehow the function converts it to a vector with as.vector and than to a matrix. The convertion to a vector works but not the one from the vector to the matrix dosen't.

Do you have any suggestions what could be the problem?

Thanks, The Captain