They feared it was a structural problem but that doesn't appear to be the case. From SpaceX

Posted December 19, 2005 at 4:40 p.m. California time: Here is the apparent cause of structural damage (further analysis may change the conclusion): Due to high winds, we placed the countdown on hold and began draining the fuel tank. As we drained fuel from the 1st stage tank, a faulty pressurization valve caused a vacuum condition in the tank. This caused a fuel tank barrel section to deform and suck inward. It is important to note that the root cause is an electrical fault with a valve, not structural design.

At this point, it appears that no other damage was sustained to the vehicle or the satellite. The rocket will be lowered down this afternoon and placed in its hangar for further inspection.