OK, I keep learning new things about this issue.
What seems to be happening, and I'm no programmer, is that if you go to fullscreen, and a certain category of target has not appeared yet, that category of target will appear black after full screen has been initiated.
What I mean by categories of targets are armed targets, armed and armored targets, camoflaged targets, and non-combatant targets. So, if I play a challenge that only has the standard armed targets and then go fullscreen, all others will appear black for the rest of my play session. If I reload the game and make sure I've played scenarios in which all target types appear they will all continue to appear properly after I have gone to fullscreen.
And yes, I think the fact that Terri Brosius is the computer voice is awesome. :)