R GUI dies using postcript() in Windows XP Pro

Dear List,

My colleague has been having a problem with the following data and 
plotting commands. The example below is part of a larger set of plots, 
but I've isolated the problem to this example using this small dataset 
(below), which kills rgui consistently. My version info

 > version

          _
platform i386-pc-mingw32
arch     i386
os       mingw32
system   i386, mingw32
status
major    1
minor    8.0
year     2003
month    10
day      08
language R

But this also happens in 1.8.1 on Windows XP Pro

The code seems to stop at the call to plot() in the code below, and then 
MS's error reporting window pops up and informs us that rgui has been 
closed.

Note that the same code, but without the postcript() and dev.off() 
commands works as expected to produce the plot on a windows device.

Any ideas as to what is going on?

All the best,

Gav

#code to run to reproduce the problem
year <- c(1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 
1998, 1999, 2000, 2001, 2002)

avgMsr <- c(10.800000, 7.000000, 6.200000, 9.571429, 10.800000, 
11.600000, 10.200000, 11.400000, 7.200000, 9.400000, 11.200000, 
11.600000, 11.600000, 8.000000, 7.600000)

totMsr <- c(19, 17, 13, 24, 17, 17, 21, 18, 13, 15, 19, 18, 21, 15, 11)

postscript(file="invert.eps", onefile=FALSE, horizontal = FALSE, 
pointsize = 8)

op <- par(mar = c(3,4,1.5,1)+0.1,font.main=16,tcl=-0.2)
plot(x = year, y = avgMsr, ylab = "Species richness", main = "Loch Coire 
nan Arr", axes = FALSE, ylim = c(0,25), xlim = c(1988,2002))
axis(2, las=1)
axis(1)
lines(x = year, y = avgMsr)
points(x = year, y = totMsr , col = "black", pch = 19, type = "o")
lines(x = year, y = totMsr)
box()
par(op)
dev.off()