[racket] Plot: plot-new-window never happens?

I was messing around with a spline utility last night and was using
the plot-new-window? setting to get a plot. The goal was to share an
exe with a coworker who doesn't have Racket. Just a command-line app
but to get the plot to display I needed a window and this seemed
awesome. The problem is I couldn't get the plot to display when the
thread was in a procedure. The window would appear but it was like the
plot backend wasn't free to draw to it. Here's a way to reproduce it
on v5.2:

#lang at-exp racket
(require plot)
(plot-new-window? #t)
(let loop ()
  (let ((dummy (read)))
    (if (and (number? dummy) (zero? dummy))
        (void)
        (begin
          (plot (function (λ(x) (* x x)) -2 2))
          (loop)))))

So long as you are looping, new windows will appear without plot
contents. When you finally quit (here by entering the number zero) all
the plots are drawn in those windows. Any help? Did I do something
horribly dumb?

Thanks,
Deren