IIS Continuously Prompts for Credentials in Unsecure Directory

Hi.  I have an intranet application accessable by users belonging to the AD group 'CustomerService'.  Inside the application is a directory named 'Unsecure' which has files available to anyone (regardless of whether or not they belong to 'CustomerService').  My web.config is shown here:
  <system.web>
    <authentication mode="Windows" />
    <authorization>
      <allow roles="MyDomainName\CustomerService" />
      <deny users="*" />
    </authorization>

    <roleManager defaultProvider="WindowsProvider"
      enabled="true"
      cacheRolesInCookie="false">
      <providers>
        <add
        ...