I got the same problem ! I bought this game just for Multiplayer.. And now i can't play it -.- I also get this Internal failure. It happens after you fill ur login pass and cd-key.
Ya, Ubisoft kinda abondoned their previous Splinter Cell games. Have you updated to 1.02? Also, Anti virus programs might be blocking, so try disabling firewalls, etc. Contact tech support if it doesnt work.