That is to be set only if you're using a proxy, otherwise don't mess with it. You said you're not using a proxy, so other than checking the domain restrictions on the computers in your test lab, I really don't know what to tell you. Have you tried running the app as a privileged user in the test lab, like some domain admin or the local computer admin? Even with such elevated permissions, the local or domain security policy might be disallowing certain things that are necessary.
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