Quote:
Originally Posted by
Philosoph 
^ What he said. During a deadlift your spinal erectors are isometrically contracting very hard, so it's not surprising that they'll feel sore. If it's a dull soreness and doesn't feel like an injury, you're probably fine.
Make sure you're keeping your back arched, pushing through the heels, and not letting the bar drift out in front of you.
You are correct here, but I would just like to correct your terminology. An isometric exercise is when you do a static exercise (like pushing the wall) and the joint is not moving. Thus, iso-same, metric-length. The deadlift is a concentric and eccentric exercise. Concentric when you come up and eccentric when you go down.