I just got a pop-up message stating that I was about to lose the game due to low war support in my war with the Huns. Well, that's messed up to start with, but what makes it totally crazy is that I am not at war with the Huns. They are an ally and good trading partner.  What the heck is going on? This seems really wrong.

You won't actually lose, the notification is bugged. It goes off whenever your war support drops to low even if you aren't actually at war. My guess is the check to see if you're at war is bugged.

Just to clarify further, I am not at war with anyone.

Exactly. You can't lose a war you're not in. War support is always present since it also affects your ability to go to war and is a rough gauge of war likelihood. The notification doesn't check to see if you're in a war or not though and gives you a "hey you're about to lose!" notification anytime your war support number gets low. Being in an alliance will always drop your war support (which makes sense), so you'll always get this bug if you stay in an alliance long enough.

This mechanism needs work.