I have experienced some problems with MDT 2010 Update 1 behind a webproxy infrastructure.
When script starts a new webservice query in ZTI_DataAccess.vbs and there is a webproxy on that infrastructure, it must be passing-through because webservice are allways in the Intranet-Zone. Therefore, on line 824, code have to be changed:
824, old -> Set oHTTP = CreateObject("MSXML2.ServerXMLHTTP")
824, change -> 'Use strict version of ServerXMLHTTP 4.0 in order to use proxy settings
825, add -> Set oHTTP = CreateObject("MSXML2.ServerXMLHTTP.4.0")
835, add -> 'Ignore proxy settings (pass-through)
836, add -> oHTTP.SetProxy 1
Without that change, webservice allways access webproxy and an error 401 or 403 is returned.