"Error occurred while decoding OAEP padding." showed when i try to decrypt an encrypted RSA text

hi guyz, the error message showed when i try to decrypt an encrypted RSA text. what does it means? how to solve it??? still confused cuz i juz copy n paste from the ebook. im using Win XP.

 the code :

  
1 Public Class AsymmetricEncryptionUtility
2 Public Sub New()
3
4 End Sub
5
6 Public Sub GeneratePrivateKey(ByVal keyFile As String)
7 Dim Algorithm As New RSACryptoServiceProvider()
8 ' Save the private key
9 Dim CompleteKey As String = Algorithm. ...