Visual Studio is not loading my debugger visualizer

Question

I wrote my own Debugger Visualizer.

It, and the attributes, are in their own assembly. There is no references or attributes in the assembly containing the class to be debugged - I want to make a drop-in dll that is optional for people to use.

The class I am trying to debug is a generic.

[Serializable]
public class FinCellTable<S> : IFinCellTable, IEnumerable<List<FinCell.IFinCell>>
    where S : class, FinCell.IFinHeaderCell, FinCell.IFinCell, new()

Here is the visualizer:

[assembly: System.Diagnostics.DebuggerVisualizer(
        typeof(Financials.Debugging.CellTableVisualizer),
        typeof(VisualizerObjectSource),
        Target = typeof(Financials.Transformation.IFinCellTable),
        Description = "FinCell Table Visualizer")]
[assembly: System.Diagnostics.DebuggerVisualizer(
        typeof(Financials.Debugging.CellTableVisualizer),
        typeof(VisualizerObjectSource),
        Target = typeof(Financials.Transformation.FinCellTable<Financials.FinCell.FinHeaderCell>),
        Description = "FinCell Table Visualizer")]

namespace Financials.Debugging
{
    public class CellTableVisualizer : DialogDebuggerVisualizer
    {
        protected override void Show(IDialogVisualizerService windowService, IVisualizerObjectProvider objectProvider)
        {
            if (windowService == null) throw new ArgumentNullException("windowService");
            if (objectProvider == null) throw new ArgumentNullException("objectProvider");

            var data = (IFinCellTable)objectProvider.GetObject();
            using (var displayForm = new CellTableVizForm())
            {
                displayForm.PopulateForm(data);
                windowService.ShowDialog(displayForm);
            }
        }
    }
}

I am running Visual Studio 2010, and the following directory contains the .dll and .pdb of the Visualizer Assembly:

C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7\Packages\Debugger\Visualizers

I place a breakpoint on an instance of IFinCellTable that is specifically FinCellTable. It does not show the magnifying glass.

I debugged Visual Studio using another Visual Studio as the first VS was debugging. I watched the output window as the first VS loaded dll's. When I triggered a visualizer on a datatable, the second VS outputted that it loaded Microsoft.VisualStudio.DebuggerVisualizers.dll and Microsoft.VisualStudio.Debugger.DataSetVisualizer.dll (the latter from the correct directory I said above). (The Modules window behaves/shows the same.)

So obviously my Debugger Visualizer Drop-In assembly is not be loaded by VS, so it doesn't know to show the magnifying glass.

How do you get visual studio to load Visualizers up-front, so drop-in visualizers work and you don't need to edit your original code?