I just re-read this post again, and this isn't the same error that you talked about above. A tool that you may use (I'm not sure if it has to be installed, or if it's in by default) is the $ORACLE_HOME/bin/oerr command to determine what the cause of an error may be.
An example of it's usage would be:
$OARCLE_HOME/bin/oerr ora 6000
to look up error ORA-06000

Hope this helps.