Does anyone know if the software that runs the Nissan Factory Navigation system is upgradable?

Note that I am not talking about the map data, but the software that runs the Navigation system itself. I have noticed a few software bugs (such as cancelling route guidance doesn't always work) and simple upgrade ideas (such as being able to easily reorder the entries in the address book) which could benefit from a software upgrade.

Also, does anyone know if the Navigation software is made by Zenrin, the company that also makes the map data DVDs for the nav system?

Thanks for your help,
-Frostpaw
2003 DB Touring Manual