Configuration under Mono?

I've got an Web.config that works fine under Windows but when I run it under Redhat I get a exception (below).

I read that is optional in the config file does anyone know why it is required in RedHat?
I created a simple test application and it does the same thing.

Please help...

------------------------ Exception ----------------
Unhandled Exception: System.Configuration.ConfigurationErrorsException: factory must be defined
at Enyim.Caching.Configuration.FactoryElement`1[Membase.Configuration.IMembasePerformanceMonitorFactory].CreateInstance () [0x00000] in :0
at Membase.Configuration.MembaseClientSection.Membase.Configuration.IMembaseClientConfiguration.CreatePerformanceMonitor () [0x00000] in :0
at Membase.MembaseClient..ctor (IMembaseClientConfiguration configuration, System.String bucketName, System.String bucketPassword) [0x00000] in :0
at Membase.MembaseClient..ctor () [0x00000] in :0
at Test.Main () [0x00000] in :0

----------------------- App.Config -----------------
<?xml version="1.0"?>

--------------------- Simple test program ------------
using Membase;
using Enyim.Caching.Memcached;
public class Test {
public static void Main() {
MembaseClient client = new MembaseClient("Default");
System.Console.WriteLine();
}
}

---------------- Simple App.config