After more investigation (ref. previous post), I have determined that the app problem can be traced to lack of backwards compatibility between 4.2 and 4.3 regarding block padding used during Java encryption/decryption. Alas, this recent Google op system upgrade caused corrupted decryption output when using text that was encrypted prior to the upgrade...this error is not the app's direct fault.
I released a fix/work-around:
"Encrypt/decrypt block padding was not backwards-compatible after Android 4.2 to 4.3 op system upgrade!!! Technically: Changed app from using AES/CBC/PKCS5Padding to AES/CBC/PKCS7Padding. This makes your old, pre-upgrade encrypted folders 'decryptable' again, but leaves brand new folders (since your tablet received an op system upgrade) undecipherable. Sorry, but this was the best of the bad options available."