Game Suddenly Ends (For All Players) Because of Karthus?

Playing Karthus jungle, for the second time in a couple of days, I suddenly disconnect and the game ends. When I reopen the client, it says that I'm not currently in a game. The same thing happens to a friend in the same game, so I assume that the game ends for all players.

Out of three karthus games and several games without karthus, the only two times this happens is when I am playing karthus and doing relatively well, around the midgame. I suspect that the issue could be items, because the one karthus game that this didn't happen with, I was so far behind that I didn't build a core set of items at all.

My items were runic echoes with boots, followed by rod of ages, and then a tear. Perhaps something is strange with the stacking interactions of tear, rod of ages, and karthus' various abilities.