OK, I was quickly testing the most recent SVN revision, not really playing the game - at least not on a serious level - and I'm not sure if this is a bug or just because I was doing unusual things to test stuff:
I wanted to see how the camera scrolled when aliens attack, so I started a battlescape mission but didn't see any aliens, just many civilians. Being impatient after a few turns of moving soldiers around, I decided to start shooting civilians, mowing them down left and right hoping the aliens would come after my soldiers instead.
While happily blasting a civ with (un)friendly fire, one soldier accidentally hit another soldier with a stray shot. Then, when clicking the "end turn" button a strange thing happened - all my soldiers started attacking each other, blasting one another in a big free-for-all!
When it got down to the last soldier left, the server crashed and I got kicked back to the geoscape - not sure what happened.
I'll post a log later if anyone wants to see it.
Perhaps one of the coders should put in a safeguard for prompting for confirmation before attacking friendly units - ("Are you SURE you want to target this unit?")
Edit: I also think the game should punish players who repeatedly "go psycho" on their own units or innocent civs that are not infected (having the funding nations get very mad very quickly, getting threats in the inbox about being removed from command, etc.).