'Catastrophic failure' using AspNetWindowsTokenRoleProvider

I'm using Windows Authentication and trying to test if the user is in a group. The code is as follows:

if (this.User.IsInRole("supervisor"))
  lblFuncao.Text = "Supervisor";

  
The supervisor group is defined in my machine. If I do not enable Role Manager, things work fine. If I change web.config to enable Role Manager

<authentication mode="Windows"/>
<roleManager enabled="true" defaultProvider="AspNetWindowsTokenRoleProvider" \>

A exception is thrown wher User.IsInRole is ex ...