How come mobs don't spawn on my server?

A few days ago I started noticing my users complaining about lack of monsters and animals. I checked and I noticed that they barely ever spawn, and when they do they're tightly concentrated. For example, like 5 pigs, 5 sheep and 5 CREEPERS together in the same area.

It should be noted that this happened during the whole 1.6 mayhem and I ran pretty much every Bukkit release in between. Perhaps there's a known bug in any of them that permanently breaks worlds?

I tried resetting my server several times, the problem persists. Sometimes it seems like the spawn rate is normal, but for the most part both monsters and animals are very hard to find. I'm running these plug-ins: Essentials, LWC, Permissions, Spyer, WorldBorder, WorldEdit, and WorldGuard. I ran the server on a test computer (with a new world) and it works fine, this is why I think the world data is messed up... Can anyone help?

Thanks in advance!

 

Go to Essentials > Config

And search for;
############################################################
# +------------------------------------------------------+ #
# | EssentialsProtect | #
# +------------------------------------------------------+ #
############################################################

If you see that, u need to search for;
spawn:
chicken: false
cow: false
creeper: false
ghast: false
giant: true
monster: false
pig: false
pig_zombie: false
sheep: false
skeleton: false
slime: false
spider: false
squid: false
zombie: false
wolf: false

If you get everything on False, everything will spawn. <Only with command, like the Giant, ghasts in the normal world.

 

Something else to try would be to see if there are a lot of mobs in another region preventing new ones from spawning. Type //butcher 1000 a few times and see how many it removes.

 

Everything was already set to false except ghasts and giants (why are there giants in the game anyways?), haha. But I don't think these settings apply as I'm not using EssentialsProtect. I only have Essentials, EssentialsChat and EssentialsSpawn. I will try installing Protect and see what happens.

The command //butcher 1000 killed 557 nearby mobs during the day. My world border is set at a radius of 500 at the very center so this must be the total number of mobs in my world... Is that too many or too little mobs for that radius? Assuming it's normal, where would these other spawn-blocking mobs be spawning?

Sometimes I take all the torches out of my mines for reusing. Is it possible that there are mobs spawning underground in these dark mines and blocking mobs spawning on the surface?

 

OK!

 

I found the problem: http://www.minecraftforum.net/topic/354266-166-mob-spawn-bug-thread/
I was able to run 20 slots on a 96KB/s since 1.6 came out... now I set the distance to 10 and everyone starts complaining about lag.

It's either lag-free but no mobs or lag with mobs.