I'm trying to disable all spawning, but still have the mobs in game for use with spawners, but evertime I edit the configs it crashes.

I've tried settting the rate to 0

and also excluding plains biomes

I get this crash report:

http://pastebin.com/cRwdmzuZ

I have fixed the crash, but if you look through the log this is the root issue:

[10:39:19] [Client thread/ERROR] [EnderZoo]: Could not load core spawn config file C:\Users\Randy\Desktop\Mine\Mulit MC\instances\ME^4\minecraft\config\enderzoo\SpawnConfig_Core.xml from EnderZoo jar: C:\Users\Randy\Desktop\Mine\Mulit MC\instances\ME^4\minecraft\config\enderzoo\SpawnConfig_Core.xml (Access is denied)
[10:39:19] [Client thread/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:-1]: java.io.FileNotFoundException:

Not sure how this is happening. You should not modify the _Core.xml file at all. All changes need to be made in the _User.xml file.

The correct way to remove the spawning is to use the 'remove' attribute. Setting the rate to 0 will not work.

Here is an example that should remove all EnderZoo spawns (I havent actually tested it):
http://pastebin.com/gcA4mNR8