Error trying to invoke a service from Net The underlying connection was closed

Hi - We are working with a team who is utilizing .Net to invoke a service on our IS v6.1. The service is established / setup as a Web Reference in .net. We are not using the webMethods .Net API.

The first time the service is invoked, the results are returned without a problem - either success or a failure as expected. The second time however, when trying to invoke the service, they get the following error, “The underlying connection was closed: A connection that was expected to be kept alive was closed by the server.” Invoke the service again, and it works fine, and then try again and the error is returned. Essentially every other time the service is called the error is returned.

I am positive that it has nothing to do with our service - we have tested, and re-tested, and tested some more, and can’t reproduce the error. There are no errors in our error logging database, or on our IS error log. I even made a .net prototype and can’t produce the error no matter how many times I invoke the service.

I have found some articles online which lead me to believe this is strictly a .Net issue and the way they are invoking the service. However neither of these solutions have worked yet:
http://markitup.com/Posts/PostsByCategory.aspx?categoryId=8
http://weblogs.asp.net/jan/archive/2004/01/28/63771.aspx

Has anyone run into the same problem, or is their a preferred method for invoking services from .Net that doesn’t produce this error?

Thanks in advance.