Running in to strange issue with the Test-Connection cmdlet, both inside a script I am writing and when running it directly from a powershell session.  No matter what computer/site I try to test I get "test-connection : Not Found"(full error text below) this occurs even when trying test-connection localhost. I am able to ping both localhost and remote computers without a problem.  it looks like someone had a similar problem a few years ago(http://social.technet.microsoft.com/Forums/scriptcenter/en-US/dad5613a-aa6e-4f0d-b99d-82d6afda83d7/bizzare-testconnection-failure?forum=ITCG) but it doesn't look like it was ever resolved and none of the suggestions in the thread worked for me. 

Test-Connection : Not found
At line:1 char:16
+ test-connection <<<<  127.0.0.1
    + CategoryInfo          : InvalidOperation: (:) [Test-Connection], ManagementException
    + FullyQualifiedErrorId : TestConnectionException,Microsoft.PowerShell.Commands.TestConnectionCommand

So what's your question?

Bill

Test-Connection is based on querying the Win32_PingStatus WMI class.  I suspect you might have a corrupted WMI repository.  There are instructions for rebuilding it on the knowledge base, I believe.  Should be easy to find with a web search.  (I'd do it, but I'm posting this from my phone.)