Whenever I play on a minecraft server, it doesn't matter how far away the player is, they could be two blocks away, but when they are running around, they keep disappearing. No one else sees it, it's just on my screen. I don't use any mods except for optifine, and I don't use a texture pack. I've tried re-launching the game several times, and I don't know what to do. I can't pvp because most of the time I can't see the player. Please help!