R gurus,
I'm having an issue with the appearance of image plots produced by R-2.13.1.  When I plot an image (example code pasted below), thin white lines appear between rows and columns of pixels.  The location of the lines seems somewhat random and change as the graphics device is re-sized.  This occurs using a range of graphic devices (windows, png, bmp, jpeg, tiff, pdf), on two different machines (windows 7-64 bit and windows XP-32 bit) but not when using 2.13.0 on either machine.  Do others have this issue?  Any possible solutions?
Regards,
Alan

x <- y <- seq(-4*pi, 4*pi, len=27)
r <- sqrt(outer(x^2, y^2, "+"))
image(z = z <- cos(r^2)*exp(-r/6), col=gray((0:32)/32))

> sessionInfo()
R version 2.13.1 (2011-07-08)
Platform: x86_64-pc-mingw32/x64 (64-bit)

locale:
[1] LC_COLLATE=English_United States.1252
[2] LC_CTYPE=English_United States.1252
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C
[5] LC_TIME=English_United States.1252

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] rj_0.5.5-4

loaded via a namespace (and not attached):
[1] tools_2.13.1

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