There are all sorts of strange things that happen if you start a new game without completely exiting the game.
Case in point:

1. In the new game I just started the fog of war around my homeworld is uncleared.
2. My homeworld approval rating is 1%.
3. I start with no starport on my homeworld.
4. The "stats" screen has a series of "string not found" in the "Overall Ranking" section
5. My ships don't clear the fog of war when they move.

The list goes on.