The Java version of Google Maps does not run properly on the Samsung BlackJack (as well as other Windows devices). Fortunately, Google has now released a native Windows Mobile version of Google Maps, and it works perfectly on the BlackJack. To download it, go to http://www.google.com/gmm on your Windows Mobile web browser, and just download the CAB file.
UPDATE: After making this post I discovered a really nice Google Maps feature. Once Google Maps is installed a new menu option is added to the Contacts application. Select any contact, and you’ll be able to select “Locate In Google Maps” to do just that. Very cool!