define('TTF_DIR','${WEBROOT}/jpgraph/ttf/');
Had to modify that a bit for mine...
define('TTF_DIR','${WEBROOT}/jpgraph-3.5.0b1/src/fonts/');
Obviously that was because of the different structure in 3.5.0b1. It still failed. Finally took a copy of Arial from /windoze/fonts/ and dumped it into the jpgraph /fonts/. That DID work, and everything on wxgraphs_test.html finally showed up.
Thanks for the tip in the right direction.