Exception occure with RSA Decryption

I'm using 'RSACryptoServiceProvider' for encyption/decrypiton. It breaks sometime during decryption, not all the time. I don't understand the reason for it, i tried some possible cause like assign permission to Crypto folder under user/applicationData, clearing machine key but didn't work for me.

The Decryption code, i'm using:

RSACryptoServiceProvider rsaProvider = new RSACryptoServiceProvider();
string privateKey = "";
rsaProvider.FromXmlString(privateKey);
byte[] DecryptedBytes = rsaProvider.Decrypt("DataToDecrypt", false);
rsaProvider.Clear();
UnicodeEncoding ByteConverter = new UnicodeEncoding();
return (ByteConverter.GetString(DecryptedBytes));


The exception:

Type: System.Security.Cryptography.CryptographicException
Message: The system cannot find the file specified.
StackTrace: at System.Security.Cryptograp ...