Error with image

I have tested http://pear.php.net/package/Image_Graph/

and it goves me error. Also on hosting service they do not know what to do.

Please help.

I have ERROR: Warning: imagettfbbox(): Could not find/open font in /usr/lib/php/Image/Canvas/GD.php on line 1240

In file logo_graph.php
is defined font:
$Font =& $Graph->addNew('font', 'Arial');

I have defined font in file logo_graph.php as they have in fontmap.txt
on server
$Font =& $Graph->addNew('font', 'Arial');

Do you know what can be wrong?

is the path to the fonts going to the right place? Only thing I can think of.