I have created a team "blue" for a map I'm working on, added via /scoreboard teams add blue. Real players who want to play will be joining via /scoreboard teams join blue @p. In addition, the teams themselves will have an overall score, tracked by the fake player "Blue" who I am trying to get to join the same way (eg, /scoreboard teams join blue Blue). However, I get "The entity UUID is in an invalid format" and the command fails. This happens when typed in chat and in command blocks. Restarting Minecraft has no effect. The same commands work fine in 1.7.10 and in 14w20b, or if I use my name instead of a fake player name. This issue also occurs when using names of players who are offline. I suspect this has to do with the recent change to players using UUID's instead of usernames in the database, but I find it strange that it occurs in 1.7.10 and 14w20b, both quite recent, and probably after the change.