I exported my wallet's private key encrypted before, and did it again today, and the encrypted keys don't match. Why is that? Is this normal?
The keys don't match? Did you decrypt the file and compared the keys inside or what do you mean? The file itself will always be different because a random initialization vector is used during encryption. This does not mean the contents (after decryption) differ. You can see what is actually inside the file by opening it with wallet-key-tool (or by manually decrypting it on the command line with openssl).
