NOTICE FOR MODS
I will be unable to play Minecraft for several months so if you could transfer the report to some other user, it'd be great.

What I expected to happen was...:
Golems would attack zombies.

What actually happened was...:
Instead they kept walking into a wall. Even if the zombies attack villagers.

Steps to Reproduce:
1. Make golem/s
2. Make zombies (if there are villagers near them they will attack)
3. The golems do nothing.

On the screenshots I used 2 golems that were naturally spawned and made some zombies near them. The zombies were bumping into the wall for a while (there was a villager near them) and 4-5sec later they found out that there is a way around the wall and just walked away. The golems went on bumping into the wall.

EDIT: As of 1.4.5 there is little difference. At times they respond instantly to new monsters, at times it takes them up to 30sec to notice them.

As of 13w06a they seem more responsive but after a while they just walk away again or pick a target somewhere far off rather than the closest one. I spawned 2 golems and a horde of zombies; they killed most but at the end they just wandered away.