If it's a new surly hub, they probably need to have the cones adjusted. Check the Feb 24 post at this link or email Surly direct if you still have problems.
http://www.surlybikes.com/surlyblog.html

Like most hubs, there will be a slight bit of compression when you tighten them down in the frame, so you compensate for this when adjusting when the wheel is off the bike.