The feasibility of a backdoor into AES with hashing and salting is laughable to say the least. Poor key selection allowing for rainbow attacks and things of that nature are operator error, not a flaw in the system. Properly chosen keys using the Rijndael implementation and salting, while it is difficult to say anything is unbreakable, humanity will have converted our species into a form of energy before you will be in any danger of attack.
The true wrench in the gears is the salting, once you start adding in random bits all over the place, you can significantly increase the complexity of brute-force attacks. And frankly, the default complexity of brute-forcing AES, even in its 128bit variety, stretches the limits of feasibility as it is.