Hi,
This is weird -- it certainly should not happen as far as 3DNA itself is concerned. I suspect that you have another program called "rebuild" in your command line search path, and it is ahead of $3DNA/bin.
To verify, try:which rebuild from your shell prompt. What do you get?
Alternatively, try to run $3DNA/bin/rebuild instead of just "rebuild".
Have a try and please let me know how it goes.
Xiang-Jun