3 Flats last week or so, including one today. I took a really good look at my Conti 4000's, and discovered that, since the last time I looked, they had really developed a shoulder, and I was near the casing on the rear. I forget that I am riding about 150 miles per week, and that does wear out tires!!
Since I got my flat right after riding on some gravel, and I spent about 15 minutes on the trail trying to find something in the tire that had caused the puncture flat, without success, I concluded that it was likely an in and out puncture. I was able to locate the hole in the tube, but there was no sharp thing in relation on the tire.
So, went to my friendly LBS and bought some Conti Ultra Gatorskins to try. Also, replaced the rim tape as a preventative measure. Hope this helps.
So, we shall see.
BTW, the LBS guy said that Specialized had totally redone the Armadillos recently, and they were a much better tire as regards rolling resistance, ability to mount and the like. Last Armadillos I had were SLOW and almost impossible to mount.