Hi gbrill,
I did some checking on this issue, and it seems like a few people have come across this particular error before. In previous instances, it was a case where multiple Target files were trying to define the same target type (Game, in this instance). Since this is happening with multiple projects, including new ones, have you added any new plugins to the Engine recently? Would it be possible to get a zipped copy of one of the new projects that you created that was having this issue?