I've gotten some tickets on the Help Desk where people are getting what they describe as either a back screen or just the Battlefront tanks firing with the black background. This happens when an element (or more) of the Upgrade is not activated. To cure it (or avoid it) follow these activation instructions:
Installation and activation instructions for the Combat Mission: Shock Force 1 Upgrade:
1) Download the game, extract the download and run the game installer.