A previous post from ScottRoy:
I can't say this will be true for your LS 430, but for my 2004, I tried pulling ECU fuses and that didn't work. When I pulled the battery negative cable off for a few minutes, then restored it, the nav system re-loaded. Apparently, there is another power line going to the ecu (to maintain the memory) that doesn't go through the indicated ECU fuses in mine. Maybe yours?
I was worried I'd loose a bunch of memorized settings throughout the car, but only lost the previous destinations list. Not bad.