Shipping by weight and state/province

I am trying to implement shipping charge by weight and state/province in NOP1.6.  I have setup the code identical to the shipping by weight and country so far.  The admin pages work fine for setting up the different rates. etc.  However when checking out I get the following error message:  

'Value cannot be null.  Parameter name='type'  

Here is the line in the file 'ShippingManger.cs' that is causing this error.  For the life of me I can't figure out why I'm getting this.  Any help is greatly appreciated.

var iShippingRateComputationMethod = Activator.CreateInstance(Type.GetType(srcm.ClassName)) as IShippingRateComputationMethod;  //line 143 in BusinessLogic/shipping/shippingmanager.cs



Bazman