MemoryStream Error: Cannot access a closed Stream

Hi,
 
I am getting error saying "Cannot access a closed Stream" while trying to return the MemoryStream object to the caller. Below is the part of the code for your review:
                Using outFs As New MemoryStream()    
                    Dim count As Integer = 0
                    Dim offset As Integer = 0
                    ''blockSizeBytes can be any arbitrary size.
                    Dim blockSizeBytes As Integer = _cryptoAl ...