Same problem
I just noticed this thread. I have had the same issue with the 38c version on Boyd Altamont rims. The first one happened with less than 20 miles on the tire. The second one happened with less than 500 miles. I run 35-50psi, depending on riding surface.
In both instances, I went in the garage and found the tire flat and half off the rim. I tried to remount but could not get the tire to seat with a pump as before. Using and air compressor, they inflated to around 35psi before popping off the rim.
Both tires were bought around the first of November from different suppliers. The first tire was replaced under warranty in November and I just submitted a claim for the second today. I just mounted my spare (from warranty) and noticed the following.
1. The two defective tires were easy to mount and inflate with a pump but almost impossible to get the bead to fully seat. After 60psi and several hours the beads fully seated.
2. The tires had a wobble when spun. Not real bad but easily noticed.
3. The warranty replaced tire went on very nicely. The tire went on the rim just as the other two with one lever to get the last little bit of bead on the rim. Inflated very easy with a pump and seated fully a lot easier than the other two.
It appears to me that the bead on the bad tires were slightly undersized (diameter) and was stretched excessively when mounted and rode. They just happened to give out in the garage and not while riding. That is a theory though. I am waiting on a response from schwalbe.