When a building is finished before another building that was started earlier is, the unfinished one won't get any more energy and stays at 99% building progress forever, unless destroyed and rebuild.
Good game, just 3 problems : You can get stuck in a lot of crap that slows you down and you can hardly see, like loose floortiles, even blocking bullets. Enemies can get "too close" for you to fire at, meaning you fire right through with no chance of survival. You can get instagibbed when something spawns right inside you
Totally, I've never actually played Dead Space ( Nor Alien Swarm ), it's Alien Breed all the way.