Yah. I had the same problem with pigs. However, the chunk error outside my house had been there a week before it started spamming pigs.
Luckily, I have MCEdit, so I got rid of at least 80%. I think they're still spawning though.
How'd you get mobs to spawn on mushroom island?
Keeps happening to me too in 1.6.2. Really annoying, but comes and goes.
Leo Schue
Yah. I had the same problem with pigs. However, the chunk error outside my house had been there a week before it started spamming pigs.