http://www.clublexus.com/forums/showthread.php?t=364641
The link is the second thread you posted. The original poster didn't fully test the system out, and he only saw the new map data and never tried to fully enter in a destination. A 7.1/4.2 disc won't let you navigate anywhere, which defeats the purpose.
Read the thread to the last page where others test it out and find the fault, which the OP admits to as well.
I realize that, I'm saying it worked for me in my wifes 06 SC430. I will check the files but the last disc I burned was v7.1 not v6.1. Either way my apologies.