This morning's 0020 SFO-DFW had a slight delay in boarding due to late arriving aircraft, and that's generally not a problem as I have a long connection on arrival at DFW. This morning, after boarding, the pilot announced that we'd be delayed 5-10 minutes while the ground crew removes the cargo that was destined for ORD. They had loaded the wrong cargo. O.K., no problem, we'll be underway shortly. Get to the edge of the Bay and we're ready to fire up the engines for departure. You would think we'd be rolling down the runway in seconds. Wrong. They determined the cargo was not properly balanced at that juncture, so we drive down the runway and exit back to the AA terminal. I believe I also overheard something about taking on more fuel from one of the other F passengers, but didn't notice that out my side of the plane. Ended up leaving the gate about 80 minutes after scheduled departure. Lot of groans about missed connections, and I saw several passengers run off the jetway on arrival to make a connection. I was fortunate to have to go only a few gates down in the A terminal and arrived just as boarding commenced for my connecting flight. Hope the trip home goes a little better. I've had three trips over the last 8 days and there's been challenges with all of them (weather, delays, cancellations, trip in vain).