PGF v2.0 manual page 46 (petri net) seems to not work

Hi all,

I'm new to PGF/tikz so I started using the manual and
the tutorials yesterday. However, I ran into trouble
with the example of the petri net. I copied all the
input on page 46 into an input file, but compilation
results in:

! Package pgfkeys Error: I do not know the key
'/tikz/on grid' and I am going to ignore it. Perhaps
you misspelled it.

See the pgfkeys package documentation for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.11    every label/.style=     {red}]

>From the log file:

(/usr/local/texlive/2007/texmf-dist/tex/latex/pgf/systemlayer/pgfsys.sty
(/usr/local/texlive/2007/texmf-dist/tex/generic/pgf/systemlayer/pgfsys.code.tex
Package: pgfsys 2008/02/07 v2.00 (rcs-revision 1.31)
(/usr/local/texlive/2007/texmf-dist/tex/generic/pgf/utilities/pgfkeys.code.tex
\pgfkeys <at> pathtoks=\toks16
\pgfkeys <at> temptoks=\toks17

so I think I have the correct installation.

Any tips? I tried searching the email lists but no
solution.

Thanks,
Wilfred

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