Try deleting sig.bin fron your GalCiv2 folder(copy somewhere safe) and relaunching. You should see a validation screen asking for your email and serial number. Enter these and click validate. This works for the CE edition sold in US.
Tennessee Trash
I had initial problems validating updates but once I got past that the game has performed fine. Describe your system.
I also had the "the product appears to be validated but the serial number or the machine SID don't match" error. Deleting sig.bin and re-launching worked for me. Thanks.
I found the answer on another thread: delete sig.bin from your GalCiv2 folder and relaunch the game. It will ask for your email and serial number. Enter and click activate. It worked for me.
I purchased CE at retail, followed registration process at SDCENTRAL and updated to 1.10X. I get the following error when I attempt to play: The product appears to be validated but the serial number or the machine SID don't match. I have uninstalled and re-installed three times with the same result. Does anybody have any suggestions?