Parameter is not valid

Hi
 I have a stream of bytes of an image. I am converting it into the image
Byte[] buffer = Encoding.Default.GetBytes(m_Stream); //   Sorry I can't paste the bytes of image because of its mammoth size)
MemoryStream memorystream = new MemoryStream(buffer);
Image img = Image.FromStream(memorystream);  
 
But on last line I am getting error.
"Parameter is not valid" 
Can anyone please tell me the reason for this.
Am I missing something.
Kindly advice
Regards
Karan 
 
 
 

 
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