Error When Registering Custom Security Trimmer to SharePoint 2010

I could use a little guidance here.  I seem to be stuck on a step that I would have thought was simple.  I've created a custom security trimmer named CustomSecurityTrimmer_POC which implements the ISecurityTrimmer2 interface.  I signed the assembly in Visual Studio in order to get a strong name for my assembly.  I created a setup application in Visual Studio that places the CustomSecurityTrimmer_POC into the GAC on the server.  I built the projects and used the .msi file to install the assembly onto the server. 

After installing the file into the Global Assembly Cache, I opened up the SharePoint 2010 Management Shell and executed code found in the Walkthrough article here: http://msdn.microsoft.com/en-us/library/ee819923(v=office.14).aspx#step2 

The code I used looked like this:

1) $searchapp = Get-SPEnterpriseSearchServiceApplication
2) new-spenterprisesearchsecuritytrimmer -SearchApplication $searchapp -TypeName ="CustomSecurityTrimmer_POC, Version=1.0.0.0, Culture=neutral, PublicKeyToken=7008d1344260eedd" -RulePathhttp://mydomain.com/directory/* -Id 1

My problem is that when I execute the second command I get an error that reads:

New-SPEnterpriseSearchSecurityTrimmer : The specified Pluggable Security Trimmer Implementation Type could not be loaded or it does not implement ISecurityTrimmer2.  Parameter name: fullyQualifiedTypeName At line:1 char:38 + New-SPEnterpriseSearchSecurityTrimmer<<<< -SearchApplication "Search Service Application" + CategoryInfo  : InvalidData : (Microsoft.Offic...SecurityTrimmer:NewSearchSecuirtyTrimmer) [New-SPEnterpriseSearchSecurityTrimmer], ArgumentException + FullyQualifiedErrorId : Microsoft.Office.Server.Search.Cmdlet.NewSearchSecurityTrimmer

Thanks in advance,