Sweave and/or beamer issue

Dear Friends,

I not sure whether this is an Sweave or a beamer problem.

The Rnw file:

\documentclass[compress,smaller]{beamer}
%\documentclass{article}
%\usepackage{beamerarticle}

\usepackage{Sweave}

\title{Psychophysics II}
\date{September 9, 2008}

\begin{document}

\frame{
\begin{Schunk}
\begin{Sinput}

 > ro <- 0.2
 > c <- seq(from = -3, to = 4, by = 0.1)
 > fn <- 1 - pnorm(c)
 > fo <- 1 - pnorm(c, mean = 1)
 > h <- fo + ro - ro * fo
 > f <- fn
 > plot(h ~ f, type = "l", asp = 1, xlim = c(0.01, 1.01), ylim =  

c(0.01, 1.01), las = 1, xlab = "p(yes | old)",
+     ylab = "p(yes | new)", main = "Dual-process model,  
p(recollection) = 0.2")
\end{Sinput}
\end{Schunk}
\includegraphics{20080909test-model}

}

\end{document}

The resulting LaTeX
***********FAILS: *****************

Runaway argument?

 > ro <- 0.2 > c <- seq(from = -3, to = 4, by = 0.1) > fn <- 1 - pnorm 

\ETC.
! Paragraph ended before \FV at BeginScanning was complete.
<to be read again>
                    \par
l.27 }

?

**********************************
But when the Rnw file starts:
**********************************
%\documentclass[compress,smaller]{beamer}
\documentclass{article}
\usepackage{beamerarticle}

***********IT DOES NOT FAIL: *****************