So here\'s the deal. I\'ve got my solution which has a few projects in it:
Is pluginTypeName using assembly-qualified naming? Is the Assembly that contains pluginTypeName showing as being loaded?
If you're using the Assembly-qualified name then .NET should be able to automatically load the assembly for you; if you aren't then I would guess that Type.GetType() is returning null since it can't locate an assembly containing the requested type.
Instead of calling Type.GetType(pluginTypeName), try Type.GetType(pluginTypeName, true). The boolean parameter indicates if the call should throw an exception in the event of a failure, instead of returning null - this way, you should get a (hopefully) better description of why GetType is failing instead of just a mysterious null!
It could be that you need to specify which assembly the type is located in:
<add key="Plugin" value="Prototypes.BensPlugin, TheAssemblyName" />