So... Here's how I got it:
sitting on Pirate planet with a Hegemony Patrol. We both attempt to engage a pirate fleet at the same time. (Hegemony fleet got priority, I only got to fight the carrier group's surviving fighters.) I'm betting the game put me into combat at the exact same time the game decided that the Hegemony fleet whipped the Pirate capitals. Anyway, after the battle, on the results screen, the "Continue" button is unclickable. Can't do anything.
This required me to terminate the game using Ctrl+Alt+Del. However, now the game's music plays endlessly in the background, forcing me to restart the system to fix it. So, that might be another bug, or something with the sound card. Not sure...
Also, is the current version of the game.