no,the heat shield material has been in use for a very long time and has proven very reliable, but they (martin? nasa?) changed various mission and materials parameters and are not bieng completly forth comming about exactly how they got in trouble.

from wiki

Thermal protection

After evaluation of thermal protection materials, NASA selected AVCOAT for the ablative heat shield. AVCOAT consists of silica fibers embedded in a resin within a honeycomb structure of fiberglass and phenolic resin. It was previously used on the Apollo missions and the Space Shuttle orbiter.