Thierry, I didn't see whether you ever solved the Metapost exit code 256 problem or not so I thought I would post my solution. I had to make sure my PATH variable included the directory where teTeX binaries were installed. In my case (Therion 0.3.9 on a more or less out-of-the-box slackware 10.2machine), I simpled added the following line to ~/.zshrc, my login script: PATH=/usr/share/texmf/bin:$PATH That made everything run swimmingly for me. Good luck! Sincerely, Jonny