This may be redundant, but have you tried taking the additional RAM out (assuming it's not from Apple); updated the firmware (caveat: third party RAM may or may not work after the firmware update); kept the first (OS X) partition to 9Gb or less; updated your drive (with either Drive Setup or the OS 9.1 Installer); verified that you are using HFS+ for the format.
Your final option may be to reformat with Drive Setup and try again (seems to be preferred Apple Tech option).