PS Remoting - Failed to connect to an IPC port: Access is Denied

I am trying to configure some deployment steps in our build process.  This involves using powershell to remotely execute MSTEST.EXE.  The remoting works fine for things like {Get-Process} or writing a file to the remote local drive.  However, MSTEST fails with the following error:

Failed to connect to an IPC port: Access is Denied

The account that powershell runs under is a domain account, and is a local admin on both the local and remote boxes.

Script looks like:
==================
invoke-command -computername BUILD01 -scriptblock {
d:
cd "D:\BuildDrop\Testing_20091210.4"
$exe = "C:\Program Files (x86)\Microsoft Visual Studio 9.0\Common7\IDE\mstest.exe"
$vsmdi = "D:\BuildDrop\Testing_20091210.4\Release\WebTests\MyProject.Tests.vsmdi"
& $exe /testmetadata:$vsmdi /testlist:AllWebTests

}
===================

I've tried using the -Credential option too, but that made no difference.  I'm not sure what security to tweak where to fix this error.

Suggestions?