NullReferenceException in System.Web.Security.RoleManagerModule.OnEnter()
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I have encountered an error for which I can find no answer online. 
I created a new virtual Server 2008 R2 Standard box with the IIS role and ASP.NET role services. The server is destined for production. I copied a website to the server and it has ceased to work; Specifically, the RoleManagerModule is throwing a NullReferenceException. This happens on any *.aspx page, but not static pages such as robots.txt. This error happens even for pages which don't have any authorization rules. Here are relevant snippets from the error in the application event log:
     
    Exception information: 
        Exception type: NullReferenceException 
        Exception message: Object reference not set to an instance of an object. 
     
    Request information: 
        Request URL: ******** 
        Request path: / 
        User host address: ******** 
        User:  
        Is authenticated: False 
        Authentication Type:  
        Thread account name: ******** 
     
    Thread information: 
        Thread ID: 8 
        Thread account name: ******** 
        Is impersonating: False 
        Stack trace:    at System.Web.Security.RoleManagerModule.OnEnter(Object source, EventArgs eventArgs)
       at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
       at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

 

This only happens if the Role Manager is enabled in the web.config as such:

    <roleManager defaultProvider="EWRO" enabled="true">

If I remove or set to false the enabled attribute, the aspx pages respond properly. I have matched as close as possible the configuration and installed services of the server on which the website is currently running. You may notice that I have a custom Role Provider, however the same exception happens even if I remove the defaultProvider attribute. The AspNetSqlRoleProvider would fail anyway, but it does not reach that point.

A solution or steps to find a solution would be much appreciated.