I went to install SH4, with the U-Boat Mission addon, on a different computer but I'm stuck at validating the key for the U-boat addon.
Many years ago I downloaded the U-Boat mission from Direct-2-Drive (I see that Gamefly has purchased D2D). When I enter my key I get the message that the key failed for "unknown reason". It does recognize an invalid key however and will give the reason as "wrong or invalid key" so the online checking sees that it is a valid key but won't authorize. It would appear that the online checking is done by Ubisoft and not D2D though. I left a message for Ubisoft but no one has responded.
Anyone left at Ubisoft?