Callout debug: Access is Denied

I'm not sure if more people are experiencing the same thing, but at least I'd like to share this information with you.After creating a debug build of a callout, I do copy the dll and pdb files to the \Microsoft CRM\Server\bin\assembly folder. Now I can normally debug the callout. But after modifying the code and copying the files again, then I cannot step into the code. CRM just steps over the