About 2 weeks ago I replaced the front rotors, brake pads and the 4 brake hoses with stainless steel ones. I noticed at that time that the rubber seal on this caliper was a bit wavery as if the piston had turned a bit, but it was still intact. I put some rubber spray on it and thought it would be ok. I also used some of that blue anti-squeal paste on the back of the pads. I believe that blue stuff is like glue and I probably used too much of it. The glue stuck to the already weak rubber and when I took the pads out this time, the rubber broke as it was pulled along with the pads. The moral: Don't use that blue stuff and don't use too much of any paste anyway...
I did not smell any burnt brakes before, but I keep an eye on all the four wheels. I touch the wheels now when I get out of the car to feel their temp. until I am certain nothing is sticking. I will do the remaining 3 calipers pretty soon. From Haasman's description and others (I did a search yesterday evening) it doesn't seem too difficult a job once you have the c-clamps and the seals etc. It was the unexpected that threw me off.
Thanks again for everybody's help