title: Error invoking COM from managed DLL via NUnit
body: <p>I have a unit test case, written in C#, wherein I have to invoke a COM object. The test case works fine, when run stand alone. The same when tried via NUnit (v-2.5.9), it fails with following exception:</p>
  
  <pre><code>System.ArgumentException: Could not convert argument 0 for call to StartInstall.
     at System.Dynamic.ComRuntimeHelpers.CheckThrowException(Int32 hresult, ExcepInfo&amp; excepInfo,     UInt32 argErr, String message)
  at CallSite.Target(Closure , CallSite , ComObject , String , String , String , Object )
  at CallSite.Target(Closure , CallSite , Object , String , String , String , Object )
  </code></pre>
  
  <p>Any clues on this weird behavior? </p>