HttpContext.Current.User.Identity.Name exception

Hi Hope someone can help.  Im getting an exception in my application when calling my custom role provider.  The roleprovider calls a sql database to obtain the users credentials using HttpContext.Current.User.Identity.Name to obtain the users login details.  


my exception log is displaying  Could not find employee ecurity.Principal.WindowsIdentity.  the ecurity.Principal.WindowsIdentity should be the login of the user in the exception message.  Also the s is missing off security.  This is not a typo.
heres my web.config
<authentication mode="Windows">
</authentication>
<roleManager cacheRolesInCookie="true" defaultProvider="DebtorRoleProvider" enabled="true" cookieName="Gifford.DebtorManagement">
<providers>
<clear />
<add name="DebtorRoleProvider" type="Gifford.DebtorManagement.BusinessLogic.D ...