Bus error on MAC OS 10.4.6

Hello out there,

we are trying to get our firebird-database to run but is not working.
Our system:
- Mac OS 10.4.6
- Firebird CS 1.5.1 MACOS (from sourceforge)

On our old system (MAC OS 10.3) it worked perfect.
Problem: The database is not starting anymore.

I found a hint on the internet and did like mentioned (in a terminal-window):
export FIREBIRD_HOME=/Library/Frameworks/Firebird.framework/Resources

And after that

export PATH=$PATH:$FIREBIRD_HOME/bin


Then they told me to do: ISQL and the Terminal says: BUS ERROR

As I'm new to 10.4.6 i dont know what the difference is.
How do I get the firebird to run?

Thanks for any help,
GB5256