I hada similar problem with a black screen ion sins start, but the mouse cursor jumped to the lefthand side of the screen.
the problem in my case turned out to be old maps, so you might want to rename the galaxy folder in drive\(documents and settings/users)\"user name"\Local Settings\Application Data\Ironclad Games\Sins of a Solar Empire to see if this fixes it, also you might want to check any old maps in the program files galaxy folder