Thanks guys for the replies. The comments regarding being in shape makes me wonder. 2 summers ago, I had been doing lots of "core" work. Planks, side planks, leg lifts, squats etc. A bunch of different excercises to strengthen the core. I don't recall having the sore ribs that summer. This summer, I got out of the habit of doing those excercises, and that is when I started having the soreness. I have just this week started getting back to doing the core excersises. Maybe I'll focus on that for 4 - 6 weeks, and see how things feel.
As far as the fit, I had previous read a bunch of bike fit information on the web. I had gone through and set my saddle height and fore-aft position according to things I had read. Tried to make sure I was at a 90 degree angle between my body and upper arns. I was feeling pretty good on the bike. But, the soreness got me wondering about reach.
Maybe it's just as simple as I had stopped doing the core work, and there is nothing wrong with my fit on the bike. At kleast not the couldn;t be overcome by keeping the core strong. I guess we will see.