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
