I am getting a C# AES Decryption "INPUT DATA IS NOT A COMPLETE BLOCK" error, but only on decryption?

I am having a hard time decrypting files using the same mechanisms that I am encrypting them with. Whenever i try to decrypt i am getting a error about how the input data is not a complete doc. Below I am going to put two files, the service provider and what is consuming it. If anyone knows why it would be giving this behavior please let me know. I have not worked with this, that much, I am adopting another project that uses it pretty heavily. I am mainly trying to figure out if it is a configuration issue or not, I am not having a problem with the encryption side of things though, which is also below. I have spent several hours trying to figure this out.

This is the service that I am using to encrypt and decrypt.

using System;
using System.Security;
using System.Security.Cryptography;

namespace Shared
{
    // AES (Advanced Encryption Standard) 256-bit Cryptography
    public class CryptoProvider
    {
        RijndaelManaged aes;
        byte[] defaultKey = { 8, 190, 2, 33, 68, 88, 11, 200, 211, 35, 68, 23, 60, 24, 223, 67, 11, 190, 165, 33, 68, 88, 11, 200, 245, 35, 68, 23, 60, 24, 223, 67 };
        byte[] defaultIv = { 11, 190, 165, 33, 68, 88, 11, 200, 245, 35, 68, 23, 60, 24, 223, 67 };

        public CryptoProvider(byte[] key = null, CipherMode mode = CipherMode.CBC) {
            aes = new RijndaelManaged();
            aes.Mode = mode;
            aes.Padding = PaddingMode.PKCS7;
            aes.Key = key ?? defaultKey;
            aes.IV = defaultIv;
        }

        public static byte[] GenerateKey() {
            var e = new RijndaelManaged();
            e.GenerateKey();
            return e.Key;
        }

        public byte[] IV {
            get { return aes.IV; }
        }

        public ICryptoTransform CreateEncrypter() {
            return aes.CreateEncryptor(aes.Key, aes.IV);
        }

        public ICryptoTransform CreateDecrypter() {
            return aes.CreateDecryptor(aes.Key, aes.IV);
        }
    }
}

This is the file is using the service above.

public static void DecryptFile(string file, byte[] encryptionKey, bool clientEcbEnabled) {
        var newFileName = file + ".tmp";
        var ext = Path.GetExtension(file).ToLower();

        using (var fin = new FileStream(file, FileMode.Open, FileAccess.Read, FileShare.Read)) {
            using (var fout = new FileStream(newFileName, FileMode.OpenOrCreate, FileAccess.Write)) {
                fout.SetLength(0);

                var mode = Cryptographer.GetCipherMode(file, clientEcbEnabled);
                var cp = new CryptoProvider(encryptionKey, mode);
                var buffer = new byte[1048576];

                if (mode == CipherMode.CBC) {
                    // write the original length of the file
                    fout.Write(BitConverter.GetBytes((int)fin.Length), 0, 4);
                }

                using (var cs = new CryptoStream(fout, cp.CreateDecrypter(), CryptoStreamMode.Write)) {
                    int bytesRead = 0;

                    while ((bytesRead = fin.Read(buffer, 0, 1048576)) != 0) {
                        cs.Write(buffer, 0, bytesRead);

                        // report progress to event if wired up
                        if (EncryptProgress != null) EncryptProgress(bytesRead);
                    }
                    cs.FlushFinalBlock();
                }
            }
        }

        File.Delete(file);
        File.Move(newFileName, file);
    }

This is the working encryption method.

public static void EncryptFile(string file, byte[] encryptionKey, bool clientEcbEnabled) {
            var newFileName = file + ".tmp";
            var ext = Path.GetExtension(file).ToLower();

            using (var fin = new FileStream(file, FileMode.Open, FileAccess.Read, FileShare.Read)) {
                using (var fout = new FileStream(newFileName, FileMode.OpenOrCreate, FileAccess.Write)) {
                    fout.SetLength(0);

                    var mode = Cryptographer.GetCipherMode(file, clientEcbEnabled);
                    var cp = new CryptoProvider(encryptionKey, mode);
                    var buffer = new byte[4096];

                    if (mode == CipherMode.CBC) {
                        // write the original length of the file
                        fout.Write(BitConverter.GetBytes((int)fin.Length), 0, 4);
                    }

                    using (var cs = new CryptoStream(fout, cp.CreateEncrypter(), CryptoStreamMode.Write)) {
                        int bytesRead = 0;

                        while ((bytesRead = fin.Read(buffer, 0, 4096)) != 0) {
                            cs.Write(buffer, 0, bytesRead);

                            // report progress to event if wired up
                            if (EncryptProgress != null) EncryptProgress(bytesRead);
                        }

                        cs.FlushFinalBlock();
                    }
                }
            }

            File.Delete(file);
            File.Move(newFileName, file);
        }