Is your N900 using Power Kernel? or Stock kernel? Run psfreedom-enable.sh and run psfreedom-disable.sh. If you see the error then it meant that your PSfreedom-enable is running. So now plug it into a turned off PS3. Pull out the power cable and press power button to kill all all left over power. Plug the cable back in, quickly press power and Eject 0.05seconds apart, keep holding eject button for a few seconds, if your PS3 takes longer to load then it will works otherwise it won't. Unplug every USB device from PS3 before you do it, and left only the N900.