VS 2010 Decrypting (text) File Failure?

Trying to decrypt a textfile is giving me an error: The input is not a valid Base 64-string as it contains a non-Base 64 character, more then two padding characters, or a non-white space character among the padding characters.Besides that I also get an exception while debugging: A first chance exception of type 'System.FormatException' occurred in Fenix.exe When I start the app it opens the file and tries to decrypt it. After decryption the string is send to a label, so I can read it. The codes I used:

vb.net
' encrypt the file Private Function Encrypt(ByVal strText As String, ByVal strEncrKey As String) As String Dim IV() As Byte = {&H12, &H34, &H56, &H78, &H90, &HAB, &HCD, &HEF} Try Dim bykey() As Byte = System.Text.Encoding.UTF8.GetBytes(strEncrKey) Dim InputByteArray() As Byte = System.Text.Encoding.UTF8.GetBytes(strText)

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