[R] Having a problem with choose.files

[Carl.Finkbeiner at tnsglobal.com]

I am relatively new to R, and am having a problem with the following
snippet of code, and I do not at all understand why it is behaving this
way.  I am running Windows XP, with R 2.12.1.

I copy and paste these 4 lines into the R Console:
  t<-c("a","b","c")
  ans<-select.list(t)
  txtNBS<-winDialogString("NBS","300")
  choose.files()

I click on OK in the Select One dialog, and on OK in the Question
dialog, and then Cancel in the file dialog.  Everything behaves as I
expect it to.  (All 3 of those dialog functions are in the utils
package.)

I then copy and paste these 6 lines defining the function fn, into the R
Console.  Note that the body of the function is exactly the same as the
4 lines above that worked well.
  fn<-function() {
    t<-c("a","b","c")
    ans<-select.list(t)
    txtNBS<-winDialogString("NBS","300")
    choose.files()
  }

When I then invoke this function by typing fn() into the R Console, I
again click OK in the Select One dialog, and on OK in the Question
dialog.  BUT, the file dialog never appears.  Furthermore, if I then
type choose.files() into the R Console, about half the time the file
dialog appears and about half the time it doesn't.  

Any help anyone can give me is much appreciated.  I cannot see what I am
doing wrong here.

Thanks,

Carl Finkbeiner