Graphs are fuzzy and distorted : Solaris 8/sparc

Hi hobbit list, after installing hobbit server on a Solaris 8 machine a couple of days ago with a couple of clients, all solaris8 / sparc I got issues with graphs generation, it gives some fuzzy results with the drawed data line, going up or down, or graphic filling with colors

It is also drawing big black X above all the legend's solid-colored squares

Here is the source code I used to build rrdtool :

rrdtool-1.2.17 freetype-2.3.0 libart_lgpl-2.3.17 libpng-1.2.15

Can anyone point me to something wrong I would have done ? I cant find any errors in apache or in hobbit logs

Thank you Yannick