error 401.2 in Failed Request Log Files

I have hosted a website with framwork 4.0 on IIS 7.5 and only window authentication is enabled.

I keep getting this log file with error 401.2 in failedreqlogfile folder.

Here it shows RequestAuthType 1 RequestAuthType Anonymous and HTTPStatus 401 and substatus 2. What I am confused about is I have enabled only window authentication and disabled anonymus authentication then why the requestauthtype is Anonymous? How to fix this error?

Thanks,