Flex :: Casting Object From ArrayCollection To Instance Of Custom Class

I am using Flex 4 and for whatever reason I cannot get the following code to work which happens inside of a ListEvent handler for a dataGrid:
_tempRule = DataGrid(event.currentTarget).selectedItem as Rule;

Rule is a custom class, and the above code always returns null. The dataprovider for the datagrid is an ArrayCollection. If I try to wrap the above code to make it like the following:
DataGrid(event.currentTarget).selectedItem as Rule

I get this error:
TypeError: Error #1034: Type Coercion failed: cannot convert Object@e15a971 to com.mycompany.arcc.business.Rule

Now I know I have done this before with native Flex classes like Button, etc, but it my case it will not work. Here is the Rule class:
package com.mycompaany.arcc.business {
import flash.utils.describeType;
import mx.collections.ArrayCollection;
[Code] .....