Check that you have a libminecraftpe.so in /data/data/com.mojang.minecraftpe/lib/. You should be able to find it inside the APK in the armeabi-v7a folder. The app might need to be installed to internal memory, too.
A lot of the copies of MCPE floating around out there have been hacked or modded in some way. I found a collection of old versions that seem untouched here, but I haven't tested all of them.