Your drive comes with a Fujitsu OEM firmware on board.
Here's the latest available Fujitsu OEM firmware (NV02):
http://www.mediafire.com/?i4feo9eld9jhqumI've also got a Lenovo OEM firmware available (NX05) and an Asus OEM one (NM02), but since they are all internally dated July 2009 (just like the NV02 one), I suspect there's nothing to gain by attempting to crossflash your drive to any of them.
If you really want to have the latest, you would need to crossflash your OEM drive it to its retail equivalent: the GH22NS40. The latest available firmware for the retail version (NL02) is internally dated October 2009 so it is the newest one available ...