The normal problem folks have is that the last map uploaded overwrites the prior upload. That happens because they don't rename the gmapsupp.img on the GPSr, before they upload a second gmapsupp.img.
But it sounds like you uploaded Arizona first, and then couldn't upload California or Nevada, but California stays there? Just a guess, but if I described your problem correctly, I'd check to see that California isn't write protected, and that there is enough room for the subsequent maps.
Are you loading the maps into internal memory or a card? Try connecting your GPSr to a computer in Mass Storage Mode and look in the Garmin folder on the card or internal memory.