Minecraft wiki entry for Reporting_Tectonicus_Bugs, associated text: Your operating system (e.g. Windows XP)
Your java version (type 'java -version' at the command line)
The version of Tectonicus you are using
The complete log file, TectonicusLog.txt which is created in the folder you ran it from
The exact command line you used
The exact config file you used
The exact location of your minecraft world you're trying to map
A complete sequence of steps you performed