This bug is quite rare to stumble upon to because I don't certainly know how to start it. If I notice the bug again in the 14w18a snapshot I will add that snapshot to the affected versions list.
I didn't find the command cause my world corrupted... But I have noticed that it happens with almost all commands. I hook up a fast clock to this command block: "/testfor @a[score_player=0]" It says "Unknown command. Try..."
Vladas
This bug is quite rare to stumble upon to because I don't certainly know how to start it. If I notice the bug again in the 14w18a snapshot I will add that snapshot to the affected versions list.