I too am getting an error trying to register my Collectors Edition game.  From what I can tell, it accepted my Collectors Edition serial number since there is a link to a download page and it said 'your collectors edition serial has successfully been registered' however there is an 'Error 4: Invalid Serial Number' at the top of the page and at the bottom it says ' Your GalCiv II Serial Number was not registered'

Sooo....am I registered with the game or not?  I am sitting here looking at the serial # on the jewel case and am sure that it is accurate unless you are also supposed to include the small SDxxxxx-xx number underneath of it.  Am I supposed to leave out or include the dashes (I left them in and it recognized/worked with the unique collectors edition serial)?  I could also try to register with the 'game of the year' version I have I guess, but that doesn't have the collectors edition stuff.

Any help would be appreciated.