It's too late to submit my game as I decided to finish it out and removed the broken fleets, but here goes:

I was fighting against two other civilizations. I had about 50 fleets of huge ships (52 logistics, so 10 per ship), stationed at my borders and protecting most of my starbases. All of my planets had moved to production as we'd finished virtually all research available. It was an arms race, with the other two weaker than I was, but allied and together probably more than a match. Without warning my logistics went to 0 and every fleet I had vanished. Instead, each had a strange icon and a name, but 0 ships, 0 logistics, and around 4,000,000,000 move points. Not kidding. When I reloaded, same problem. The AI suffered it too, but much more limited. In one turn I had lost nearly 80% of my military forces and was quickly destroyed by my suddenly much more powerful enemy. Fyi: This happened a turn after getting the "disease" mega event.

Anyone else ever experience this? Was there a way to get your ships back?