Is there a way to write to a memory stream, in a medium trust enviroment?

I am working working on the early release of Azure from Microsoft and am not able to write to a memory stream. Keep getting an exception. I fixed the issue by using a different technique to achieve my end goal, however I wanted to know if there is a way to do it. Given that Azure is a shared infrastructure I cannot change the security level.

From stackoverflow

• There shouldn't be any medium trust issues with writing to a MemoryStream. How are you writing to it? What's the exception?

• I will try to reproduce it. I was doing it on the dev fabric of window's azure. Simply wanted to serialize an object to memory.