Hi,
Since your version is 9.0 PL8, you cannot change the sa password after the installation - I assume you provided its credentials when installing the System Landscape Directory. I advise you to change the password back and reset it in the System Landscape Directory; if it doesn't work, you'll need to reinstall the System Landscape Directory.
Unless you upgrade to PL13 or higher, there'll be a configuration tool to update the password; before PL13, changing the database user password used for installation simply disconnects the System Landscape Directory from SQL.
Best