Also are you running a windows UI alteration program such as Windowblinds? If so set the program to not skin Galciv.exe and galciv launch.exe
This is one of the primary issues i have found for your trouble.
You should also open the file 'prefs.ini' in your my docs/my games/GCII folder and look for the lines: -
DisplayWidth=1280
DisplayHeight=1024
The numbers may differ but make sure they are no smaller than the screen resolution you are running (you can change the resolution in the game later). Once you have altered the above save and then try running the game again.
Hope that helps in some way. If not then post your debug.err as Kryo suggested and we can look into it more for you

Drengin