R help - Apr 2011 - Error in png: unable to start png() device

Hello.  I have made many pngs in the past, but started having trouble with
them yesterday.  I just downloaded R 2.13.0 this morning, and was able to
make some pngs earlier this morning.  Now I am trying to remake them, but
get the same error message I got yesterday:
> u='in'
> w=10.5
> h=8
> png('winbugs changepoint graphs ind hibs gt 400
p%02d.png',height=h,width=w,res=300,units=u)
Error in png("winbugs changepoint graphs ind hibs gt 400 p%02d.png",
height
= h,  :
  unable to start png() device
In addition: Warning messages:
1: In png("winbugs changepoint graphs ind hibs gt 400 p%02d.png",
height h,  :
  Unable to allocate bitmap
2: In png("winbugs changepoint graphs ind hibs gt 400 p%02d.png",
height h,  :
  opening device failed

This exact same script worked an hour ago!  I have tried closing R and
re-opening it, but I am getting this error message every time now.  I cannot
make any sense of this, and the posts that I have found have not helped.
One said that I could use bitmap(), but then I would need to install
ghostscript, and I don't have priviliges to do so.  If anybody knows how I
can fix this, I would really appreciate some guidance.

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I don't know if anyone is reading this, but I have more information now.  I
can run the same script on my other computer over and over, change the
height, width and res, and it works every time.  But on the faulty computer,
I can open R, open the script, and run it and it works.  I can re-run it any
number of times and it works.  However, when I change the height, width, or
res settings in the function, I get the error message.  From that point on,
even if I change the height, width, or res back to what worked before, it
will no longer run and I get the error message.  I can only get it to run
again by shutting down the program, re-opening R and the script, and running
it again.  This is just bizarre to me and I have no idea why I am having
this problem.  Thanks if you are still reading, and I welcome any input.
I'm not very technically savvy, but I am running it on Windows XP Pro
Version 2002, Service Pack 3.

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>? I post using html because that is the only way I know
> how, that is, I send an email to r-help at r-project.org.
This message was sent from gmail. It is trivial to do so.
Failing to look around the interface is just a sign of ....
failing to look around.

Notice  there is no html mail deleted message.

-- 
David