Zombies that fixate on villagers in the area totally ignore player regardless of how close the player is to the fixated zombie. I have walked up to several zombies, which were fixated on villagers in a house, and I pushed them around but took no damage. This also occurred with a zombie that was much closer to me than to any villager (about 40 blocks away and 3 blocks higher than the villager). The zombie came up to me, did no damage, started walking away from me toward the villager. So I hit it with my sword. The zombie then became fixated on me and began doing damage. I killed it.
Environment
OS: win 7 64 - bit
RAM: 16Gb
Java: "1.7.0_21"
Java(TM) SE Runtime Environment (build 1.7.0_21-b11)
Java HotSpot(TM) 64-Bit Server VM (build 23.21-b01, mixed mode)
Graphics card: Raedon 5770
Also I can't seem to get an Enderman to try and kill me. I am standing under a two block high by 2 block wide overhang when I look at them. I hear the noise but then it stops and no Enderman comes even though I continue looking at it. Is this normal behavior?