[ESS] Command prompt disappears after function evaluation and line evaluation (bug?)

[Leo Alekseyev]

Hi all,
I discovered an annoying behavior in ESS 5.3.10 with R 2.8.0 and Emacs 22.3.1.

After I send a function to the buffer in the course of "evaluate
region", the buffer prompt will contain something like this:
> + + + >
If I now accidentally try to evaluate this line by going to the
beginning (C-a) and pressing return, I lose the command prompt, and
can't get it back until I kill the process.  To reproduce: mark the
following R function and send it to the ESS process using
eval-region-and-go, then press C-a and return.
foo <- function(){
  cat("Is this a bug?  Mark this fn and M-x ess-eval-region-and-go")
  cat("Now press C-a RET and the command prompt will be gone")
}
Expected behavior: a possible error/warning and return to command
prompt.  Observed behavior: command prompt disappears, and attempts to
edit the buffer result in "Text is read-only" message in minibuffer.