Error message: "Cannot add the specified assembly to the global assembly cache" or "w3wp.exe unhandled exception (System.UnauthorizedAccessException)"

Hi,

The Business Connector proxy account might not have the appropriate permissions on the server to allow access. The Business Connector proxy must:

• Be a user in Active Directory.
• Be a member of the Power Users, IIS_WPG, STS_WPG, and the Performance Monitor Windows groups on the server that runs IIS and hosts Enterprise Portal

Create a user with domain in active directory

Also in administrative too you can find above list of members in user in that properties add the member tab Domain / user that you created as business connector proxy

regards