Looks like there may be a new, updated GM NAV DVD disc out. Folks are advertising them for sale on eBay:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">United States/Canada DVD-ROM Map Disc
Version 4.1, 04R4
GM Part Number #: 15792651
</div></BLOCKQUOTE>
Maybe Partsman can verify this works with our NAV units and give us a price.