Trying to access VB.Net dll from excel get 429 error

[bonkey]

I am trying to create a DLL in VB.net to parse a very large XML file.
By Large I mean it takes excel 3 hours to open it. I have my own XML reading code that can deserialize it in an hour. In VB.net the built in deserializer can deserialize it in a few minutes.

So, I make a simple DLL (hello world) app and make sure i can register it and use it in excel and I can.

Then I start adding my custom code.

Little by little I add code and test, add code and test.

Eventually I get error 429:

Run-Time error '429':
ActiveX component can't create object

Once I get this error I am toast. I can never run my code again without getting this error.

I unregister the DLL. I deselect it from excel. I clear all references in the registery. I even rebooted.

How can I clean up after the 429 error and get my code working again?

Here is my basic hello world code

Imports System
Imports System.Collections.Generic
Imports System.Text






Namespace DotNetLibrary
    Public Class DotNetClass
        Public Function DotNetMethod(input As String) As String
            Return "Hello " & input
        End Function
End Namespace