Please, more info... where have you buy Sins of Solar Empire ? ... What version ( not sure if it is true but i have read that Kalypso have loose a CD with a bunch of serial key and result was that a lot of sins serial was rejected at registration )... where have you try to activate the serial ? A game buy on Impulse cannot be activated on Steam by example...

Don't know for sins but in the case of some other game, serial cannot be registered because it is already registered by somebody who have generated a identical key that yours with a illegal key generator software...

Simply contact stardock sales dep, with evidance of your purchase and they will help you... customer service of Stardock is usually good and fast...

Anyone having serial number issues, please contact [email protected] with your serial number, where/how you purchased the game, and any email addresses you regularly use.  We will straighten it out for you, but we generally can't do that through the forums, as it may involve personal information.