This is an error happens on the Langerhans dogecoin wallet. recently clients reach us for this problem. this is not a common problem but mainly happened for the wallet key backup made around Jan, 2014- Feb 2014. there are generally 3 possible reasons for different cases (although there is same error there are many different reasons for this) we need evaluate each case one by one. reason 1: password is wrong. 2. the protocols conflict. 3. wrong encryption process when you do makeup.
solution: 1. to verify the password you hold to make sure it is correct.
2. try to modify the backup to make it readable by new protocol
3. Decrypt the backup with our own script and method