Thanks for your reply Scott. Yes we have checked the settings on the Connections tab of Internet Options. We have actually sifted through all the settings on the DUN connection, then modem, etc and none of those seem to have changed. Also, when the user connects to the internet, everything works as it always has. Just seems that the calls to WININET.DLL to specifically dial the DUN connection and then to disconnect at the end of the session both fail now. Other calls to WININET.DLL are still working though which is confusing...