**Just wanted to let anyone know who was having the same issue, it was
caused by the order that things are rendered on a wiki page.
The fix (at least temporarily) was to go into the xwiki.cfg file and edit
the line containing the order which files are rendered.
I changed the line :
# xwiki.render.renderingorder=macromapping, groovy, velocity, plugin, wiki,
wikiwiki
to this :
# xwiki.render.renderingorder=groovy, velocity, macromapping, plugin, wiki,
wikiwiki
And now it works. I'm assuming its because the page tried to post the chart
before it was rendered.
My charts work, all is well.
Adam