Access is denied occurs when the webservice does not have permission to access the location of the Atalasoft dlls. The problem is that ASP.NET caches our dlls to another folder, and that’s where it needs access. 

NOTE: While placing Atalasoft DLLs in the GAC may resolve the immediate access denied issue, we strongly recommend against using this approach.

There are two solutions for this issue:

1. (PREFERRED) Grant the pertinent user READ/WRITE access on the "C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files" Folder. Pertinent user is most likely the ASP.NET/Network service user and anyone you might be impersonating
2. (DEPRECATED) Put our dlls in the GAC. The license file cannot be in the GAC and you will need to edit the registry so that it can be found.

http://www.atalasoft.com/KB/article.aspx?id=10235