Microsoft.ReportViewer.Common gives "Access Is Denied" error

Using .NET 4.0, I have a small ASP.NET app that utilized the ReportViewer object, I have created a web page that takes some user input and generates a report that is displayed using the ReportViewer control with ProcessingMode set to local.

Naturally, it works perfectly when run via VS 2010 in debugging mode and if I publish it to IIS running on my local machine. However, when I push it to production, I get the following error whe开发者_JAVA技巧n actually trying to run the report

For the image impaired:

Failed to load expression host assembly. Details: Could not load file or assembly 'Microsoft.ReportViewer.Common, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. Access is denied.

I have verified that the assembly (as well as the other reportviewer dependencies) is in the GAC. There don't seem to be any errors in the event log on the server.

Any ideas what the permission problem might be?

What authentication are you using in IIS? (e.g. windows, anonymous, ASP.NET impersonation)

As it happens, the production environment I was deploying to is a web farm and the virtual directories point to a location on a network drive. When I tried deploying to a non farm server, with a virtual directory located on the server itself, this worked. The permissions are identical in the two environments, so I can only assume that something about this control didn't like being located on a different box than IIS and ASP.NET.

I'm not sure if this is actually an "answer", so apologies in advance if I've handled this wrong from a stackover perspective.