/scoreboard players does not work

I am working on a map, and I use the scoreboard command a lot. I have a villager named Nexus right next to command blocks that change its score. When I try to add a score, or reset it, or any /scoreboard command in general, the game does nothing. I check the console, and there is no error message, or any indication that I have used the scoreboard command. My client is fine, I can place and destroy blocks like normal, and if I say anything in chat, it shows up in chat. I have cheats enabled, but the scoreboard command does not work. The same thing happens with command blocks.

Yes, I know that there have been other bugs like this posted, but they were from 1.7 and previous, and have been "resolved". this is the only 1.8.4 scoreboard command bug that I could find.